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Grandmas Lancaster Sour Milk Cake Made Keto with chocolaty buttercream frosting!

Updated: Jan 16

This delicious cake was a fan request from a patron of mine. But not just a patron but my Uncle Gary who recently went keto after my mother and I explained the keto diet to him and he was intrigued, being in the medical field his whole life and never hearing about it. He is really enjoying it and became a patron soon after going keto. The funny thing is, he requested a dessert that he had as a child along with my mother, who had the recipe and I had already grabbed it from her to make keto last year but was unsuccessful then. Thought this was the perfect time to tackle it again now that I know more about keto baking.

Every other keto vanilla cake I tried came out dry or grainy and crumbly. I wanted a moist, soft, tall cake layer that stayed together if I wanted to slice it into extra layers. I made the cake batch big enough to give substantial layers like a regular cake would yield. To get that I could use the same ingredients as the original recipe besides the flour and sugar and just up amounts to get the lift and volume I wanted.

The sugar can be substituted with any alternative sweetener but I would suggest blending up granular to get a more powdered sweetener because it will help the texture stay soft and smooth. I used powdered erythritol/monkfruit blend and it turned out perfect. If you prefer sweeter cakes I would put some stevia extract into the cake batter, with the liquid ingredients. The frosting is pretty sweet so the cake doesn't need to be overly sweet.

The flour for keto desserts is very tricky, I believe the best combination is coconut flour and unflavored whey protein. It gives a soft non-grainy texture and cuts the carbs way down. Then adding in xanthan gum makes it so its like a regular cake that doesn't fall apart and get crumbly on you. Most gluten free all-purpose flour substitutes have multiple flours and additives to make them similar to the gluten filled all-purpose flours.

I also found the best way to mix keto cake batters. Whipping up the room temperature eggs until fluffy then adding in all the rest of the warm wet ingredients creates the fluffy airy texture. Then adding in the sifted and whisked dry ingredients in one batch and hand whisking just to combine and get all the lumps out makes for a not tough cake. And its easier to pour quickly before it thickens too much from the coconut flour absorbing all the liquid. I weighed the batter into each 8 inch round to about 520g each which made sure the layers would be even.

In order to make these desserts it is really important to weigh the ingredients. They are so light and can easily be to packed down or not packed enough and can be 40-100 g difference between cups. Its kinda crazy, I couldn't get close to the grams with using measuring cups. I put the cup measurements that went along with the weights and measurements on the back of the packages.

Oh and I have no idea why it's called Lancaster sour milk cake. Mom and Uncle said it may have to do with where my family lived at the time she started making it. But all I know is that it was a delicious non-keto cake when I was growing up and I'm glad to be able to make it again so I can have it now!

Keto Lancaster Sour Milk Cake:

80 g Powdered Sweetener (2/3 Cup)

102 g ISOpure Protein Powder (approximately 3 1/2 scoops)

128 g Coconut Flour (1 Cup)

3/4 tsp. Xanthan Gum

2 1/4 tsp. Baking powder

1- 1/4 tsp. Baking Soda

1/8 tsp. Salt

5 Eggs (room temp)

1 -1/4 Cup Alternative buttermilk (1 Tablespoon Vinegar + unsweetened almond/cashew/macadamia nut milk) warmed in microwave

10 Tbs. Butter (melted)

2 Tbs. Vanilla Extract


1. Make the homemade buttermilk, pull out eggs and melt butter

2. Preheat oven to 350 degrees and grease and line the bottom of 2- 8 inch or 9 inch cake pans

3. Weigh/measure and sift all dry ingredients and whisk everything together well

4. If eggs aren't room temperature, soak in some warm water until no longer cold, crack into a large bowl and whip with a hand mixer until light and fluffy, double in volume

5. While whipping, stream in the melted butter then the warmed buttermilk and vanilla

6. Switching to a hand whisk, mix all the dry ingredients into the egg mixture

7. Divide batter evenly between the 2 prepared pans (about 520g each) and smooth out the top with an offset spatula

8. Bake on middle rack side by side 20-25 minutes, spinning and rotating them half way threw baking

9. Test with a toothpick in the center, to make sure it's not gooey and press gently to see if it is firm in the middle, they both may not be done at the same time

10. Let cool on a wire rack in the pans until cool enough to handle

11. Run an offset spatula around the edge of the cake pan and turn out onto the wire rack to cool completely

12. Make the FROSTING! (my favorite part)

Keto frosting is very easy to make. Just butter, powdered sweetener, flavoring and milk or water to make spreadable. I made this frosting extra chocolaty because that is how my uncle described it and I loosely followed my grandmothers recipe. Which I assumed is the one that she used for this cake when my mom and uncle were growing up. But according to my mother she never really measured anything so I had to assume the amounts of some ingredients. The amount of powdered sweetener used is determined by how sweet you want your frosting.

Keto chocolate frosting: You can make as much or as little frosting as you want! To do a 4 layer cake I needed another 1/3 of a batch of frosting.

3/4 Cup Softened Butter (I use salted to cut the sweetness) 12 Tbs.

2-3 Cups Powdered Sweetener (I prefer monkfruit/erythritol blend, it's less cooling than straight erythritol)(sweetness level is up to you)

3/4 Cup Cocoa Powder

Warm Alternative Milk or water a few tablespoons added slowly to create a spreadable frosting

2 tsp. Vanilla Extract

Pinch of salt


1. Whip the butter with the paddle attachment in the stand mixer (can use a hand mixer) until light and fluffy

2. While the butter is whipping, sift the powdered sweetener, more than you think you will need and sift the cocoa powder into another bowl

2. Add in the powdered sweetener a little at a time, scraping down the bowl after each addition, whip until fluffy and smooth

3. Add in the cocoa powder and beat until smooth

4. Add in vanilla extract

5. Slowly add 1 Tablespoon at a time of the warm milk into the frosting until the right consistency is achieved

Can keep frosting in a Tupperware container in refrigerator for a few week.

If using 8 inch round cake pans you can easily slice each cake into 2 layers and build a 4 layer cake. You can still make a 4 layer cake out of the 9 in cakes but it takes a skilled hand to slice the cake layers in half. This is more of a restaurant style way of building a layer cake, a little fancy.


Place a small swipe of frosting onto the serving platter you are using and lay down your first layer of chilled cake. Spread an even layer of frosting all the way to the edge, if using thinner layers of cake make the frosting a little thinner. Place next layer and repeat until all the layers are assembled. Cover the cake with a thin layer of frosting to trap all the crumbs so they don't end up in the final layer this is called a crumb coat. Chill in fridge for about 10 minutes until the frosting is set. Once chilled spread another thin layer around the whole cake and decorate however you desire! Slice and serve right away or cover and refrigerate for a week. Let come to room temp. before serving. Or heat and serve with keto ice cream or freeze for later treats!

Macros: for 1/12 of the cake-can be easily cut into 16

339 Calories

31 g Fat

9 g Total Carbs

7 g Fiber

2 g Net Carbs

13 g Protein

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Aug 18, 2022

OH...MY...Goodness. Our 15th anniversary is August 25, 2022. I'm going to surprise my cake loving keto hubby with this cake!

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