One of my all-time favorite desserts is crumb cake. Entenmann’s crumb cake, specifically. When I left New York, I quickly discovered that “crumb cake” as I’ve come to know and love wasn’t really a thing everywhere- in most places, it’s referred to as coffee cake.

Flavor-wise, a crumb cake and coffee cake are virtually the same thing. But the major difference is that a traditional New York style crumb cake is made up of a majority of crumbs, vs a coffee cake that has minimal crumb topping.

And let’s be honest… the crumbs are the best part. So we should absolutely overload our cake with crumbs! We’ll consider this mug cake a hybrid, and since my beloved Entenmann’s calls it a Crumb Coffee Cake, that’s what we’ll do as well!


The ingredients

As I write this, we’re in the midst of a global pandemic. Because of this, the supermarket has pretty slim pickings, especially down the baking aisle. You pretty much can’t find any flour, but I did find plenty of cake mix! I opted for a sugar-free cake mix, but any cake mix will do. The sugar-free cake uses Splenda, so if you’re not about that sugar alcohol life, grab yourself a regular cake mix! I do suggest getting a yellow cake mix for the most authentic flavor, though.

Our cake is going to be made of just two ingredients: cake mix and soda. Seriously, that’s it! One of my favorite baking tricks of all time is replacing the eggs & oil in your cake with diet soda. It sounds crazy, but it produces a very similar result! I used club soda here for the mild taste, but any soda you have on-hand will work. Even if it’s not diet, that’s totally fine. We’re only using 2 tablespoons, so the caloric impact is going to be pretty much non-existant.

I do suggest sticking with a light soda like seltzer or 7-Up. If you only have Coke or Pepsi, they’ll work, but you’re going to get a slightly different taste, and likely a bit of a brown colored cake.

Quick side note: whoever decided to name that cake mix “Moist Supreme” needs to be fired. Moist is gross sounding as is, we don’t need supreme moist.

To help us infuse some flavor into our cake, I mixed some maple syrup and cinnamon as a little cinnamon swirl in my cake. This step is totally optional, and not necessarily commonplace when it comes to crumb cake, but as you can see in the photo of my final product, it really helps give you that beautiful cinnamon swirl finish.


The crumb topping

The crumb topping is where you have some room to experiment if you don’t have all the ingredients you need.

The dry ingredients are vanilla whey protein, oat flour, cinnamon, and brown sugar. A traditional crumb topping is basically just flour, sugar, and butter, so I wanted to utilize some whey protein instead. The problem with whey protein however, is that it is super sticky. To combat this, I paired it with oat flour, which is very absorbent. Don’t have oat flour? You can make your own by throwing some oats into a food processor or spice grinder, or you can swap it out completely for regular flour.

I used light butter for this recipe to save on some calories, but feel free to stick with regular butter or your favorite butter substitute. I did try applesauce in place of butter, and while it did work, the crumb ended up being very dry, so just keep that in mind.

No brown sugar? No problem! I recommend it get you the most authentic crumb topping, but regular sugar will work as well.


The beauty of a mug cake

If you’ve never made a mug cake, you’re in for a treat. It is the easiest thing EVER. All you do is mix your ingredients, spray a mug with nonstick spray, fill ‘er up, and microwave for a minute. Then you’re done!

You can use any size mug you want, but I just stuck with a standard coffee mug. It was only filled about half way, but don’t worry, it will poof up to the top in the microwave! If you use a wider mug, it won’t poof as high, but will still work just as well.

For the final product, I slid the cake right out of the mug for plating. But one of the best parts of a mug cake, outside of how easy it is to make, is that you can eat it right out of the mug!

Now let’s get into it…


High-Protein Mug Crumb Coffee Cake

High-Protein Mug Crumb Coffee Cake

Yield: 1 Mug Cake
Prep Time: 1 minute
Cook Time: 1 minute
Total Time: 2 minutes

An authentic NY-style crumb cake ready in under 2 minutes!


Ingredients for Cake

  • 42g (1 Serving) Pillsbury Sugar-Free Yellow Cake Mix
  • 2 tbsp Diet Soda of Choice
  • 1 tbsp Sugar-Free Maple Syrup
  • 1 dash Cinnamon

Ingredients for Crumb Topping

  • 15g (Roughly 1/2 Scoop) Vanilla Whey Protein (I used Bowmar Nutrition)
  • 15g (2 Tbsp) Oat Flour
  • 10g Brown Sugar Substitute (I used Swerve)
  • 1/4 tsp Cinnamon
  • 14g (1 Tbsp) Light Butter
  • Powdered Sugar Substitute for Topping


  1. Start by making the crumb topping. Combine the whey protein, oat flour, cinnamon, and brown sugar in a bowl. Add the butter, and then use a silicone spatula to mix it all up, pressing to incorporate all the butter. It’s going to be pretty dry and crumbly, but keep mixing it together. You can use your hands if it’s easier! You should be left with some large crumbs and lots of smaller ones- that’s exactly what we want. If it seems too dry, add in a dash of vanilla extract for extra flavor and moisture.
  2. In a separate bowl, make your cake by stirring together the cake mix and soda until smooth.
  3. Generously spray a mug with nonstick spray (don’t be shy!) and add half of your cake mix.
  4. In another small bowl, whisk or stir together one teaspoon of maple syrup with a dash or two of cinnamon. Add it to your mug with half the cake mix and swirl it around with the spoon.
  5. Add the rest of your cake mix on top of the cinnamon swirl.
  6. Sprinkle your crumb topping over your cake. I used about 3/4 of the topping and saved 1/4 for the end.
  7. Microwave for 45-60 seconds, depending on your microwave strength. Don’t be afraid when it poofs up- that’s going to happen! It will also depend on your mug size, but one minute should work great.
  8. Slide the mug cake out onto a plate (you can use your silicone spatula to loosen it away from the edges if necessary) or enjoy directly in the mug. Sprinkle the rest of the crumb topping over the cake, top with powdered sugar, and dig in!


Contains 19g sugar alcohol

Nutrition Information
Yield 1 Serving Size Mug Cake with Crumb Topping
Amount Per Serving Calories 285Total Fat 7gCarbohydrates 49gFiber 2gProtein 15g

Did you make this recipe?

Share your final result and tag me on Instagram!


Final note: I don’t count the carbs from the brown sugar substitute or confectioners sugar (both Swerve products). Since they have no caloric value, I do not count them towards the total. The sugar alcohol in the recipe come from the cake mix.

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