This low carb chocolate mug cake is warm, fudgy and ready in about three minutes, start to finish. A spoonful of flaxseed meal and a little almond flour give it a soft, tender crumb, and a pinch of cinnamon makes the chocolate taste even richer. At about 5g net carbs, it's a keto-friendly treat for one.
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I have such a soft spot for mug cakes. They come together in one jug with hardly any mess, and they're built-in portion control: when you bake a whole cake, you just know you're going to go back for a second slice. This one scratches the chocolate itch on a weeknight without any fuss, and it's filling enough that one mug really is plenty.
Key Ingredients & Substitutions
- Flaxseed meal. This is the secret to a flaxseed mug cake that doesn't taste "low carb." Ground flax adds a gentle nutty flavor, helps bind the batter and keeps the cake moist instead of spongy. It's also where much of the fiber comes from: the whole mug cake has about 6g of fiber and 5g net carbs. Buy it already ground (I like Spectrum ground flaxseed), since whole seeds won't blend into the batter. Golden and brown flax both work; golden is a little milder. Keep an open bag in the fridge or freezer so it stays fresh.
- Almond flour. Use finely ground blanched almond flour for the softest texture. Almond meal (with the skins) works too, but the cake will be a bit denser and grainier.
- Egg. One large egg gives the cake its structure. There's no good swap here, since it's doing most of the work.
- Sugar free syrup. A monk fruit sweetened syrup such as Lakanto simple syrup sweetens the cake and keeps the batter loose. You can also make your own low carb simple syrup. Liquid stevia works in a pinch, but use just a few drops and add a tablespoon or two of water so the batter isn't too thick.
- Cocoa powder. Plain unsweetened cocoa powder is all you need. Dutch-process cocoa gives a darker, smoother chocolate flavor if you have it.
- Coconut oil. Melted coconut oil keeps the cake tender. Refined coconut oil has no coconut taste; melted butter is a great swap.
- Cinnamon and baking powder. Half a teaspoon of cinnamon adds warmth without shouting, and baking powder gives the cake its lift. Leave the cinnamon out if you'd rather have a plain chocolate cake.
Helpful Tips
Mix in a jug, then pour. You can stir everything right in the mug, but I get a smoother cake when I whisk the batter in a small jug first (a Pyrex measuring cup is perfect), where there's room to reach every dry pocket.
Pick a big enough mug. Use a microwave-safe mug that holds at least 10 to 12 ounces, so the batter only fills it about halfway. The cake puffs up as it cooks, and a small mug can bubble over. A wide, straight-sided stoneware mug cooks the most evenly.
Start with 60 seconds, then go in short bursts. Microwaves vary a lot. In my full-power microwave the cake is done in one minute, but a lower-wattage oven may need up to 90 seconds. Cook it for 60 seconds, check, then add 10 to 15 seconds at a time until the top looks dry and springs back when you press it. A slightly soft center is fine; it keeps cooking as it rests.
Don't overcook it. Almond flour cakes go from moist to dry and rubbery quickly. If you're unsure, stop a few seconds early. You can always pop it back in.
Let it rest for a minute. The mug will be hot, and the cake firms up and tastes more chocolatey after a minute's rest. It's the hardest minute of the whole recipe!
Variations
- Molten middle. Push a square of sugar free dark chocolate into the center of the batter before cooking for a gooey, lava-cake center.
- Mocha. Stir half a teaspoon of instant espresso powder into the dry ingredients.
- Peanut butter swirl. Drop a teaspoon of natural peanut butter or almond butter on top of the batter and swirl it in with a knife.
- Mexican hot chocolate. Keep the cinnamon and add a tiny pinch of cayenne for a little warmth at the end.
- Different flavors. Skip the cocoa and try my Low Carb Lemon Mug Cake or Low Carb Funfetti Mug Cake instead.
Serving Ideas
Eat it straight from the mug while it's warm. A spoonful of whipped cream melting over the top is my favorite, but a scoop of low carb vanilla ice cream, a dollop of Sugar Free Marshmallow Fluff or a drizzle of Low Carb Caramel Sauce are all great too.
A few fresh raspberries or sliced strawberries on the side add a bright, tart contrast to the chocolate. On a chilly evening, it's lovely with a cup of coffee or a mug of Low Carb Nutella Hot Chocolate if you're really leaning into the chocolate.
Storing & Freezing
Mug cakes are best eaten right away, while they're warm and soft. If you can't finish it, cover the mug and keep it in the fridge for up to 2 days, then warm it for 10 to 15 seconds before eating. You can also mix the dry ingredients ahead of time and keep them in a small jar, so all you need to do is add the egg, syrup and oil.
I don't recommend freezing a cooked mug cake, as it turns dry and crumbly once thawed. Since it only takes a few minutes to make, it's much better to whip up a fresh one whenever the craving hits.
More Low Carb Chocolate Treats
If you loved this recipe, here are a few more you might enjoy:
- Low Carb Hot Chocolate Mug Cake
- Low Carb Brownie Bombs
- Low Carb Chocolate Dump Cake
- Keto Hot Chocolate Bombs
- No Carb Desserts
📖 Recipe
Low Carb Chocolate Mug Cake
Ingredients
Equipment
Step-by-Step Instructions
- If your coconut oil is solid, melt it in the mug you plan to use (about 15 to 20 seconds in the microwave), then pour it into a small jug or bowl. The thin film left behind greases the mug.
- Add the egg and syrup to the melted coconut oil and whisk with a fork until smooth.
- Add the almond flour, flaxseed meal, cocoa powder, cinnamon and baking powder. Whisk until there are no dry streaks.
- Scrape the batter into the greased microwave-safe mug (at least 10 to 12 oz, so the batter only fills it about halfway).
- Microwave on full power for 60 seconds. The top should look dry and spring back when pressed. If the center still looks wet, microwave in 10 to 15 second bursts until set (most microwaves need 60 to 90 seconds in total).
- Let the cake rest for 1 minute, then top with whipped cream, if using, and dig in with a spoon.
Nutrition
Notes
Tried this recipe?
Let us know how it was!Nutritional information is provided as a courtesy and is my best approximation. Net carbs are calculated as the total grams carbs minus the total grams of fiber.
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