Snack

Peanut Butter Whey Mug Cake

Name: Peanut Butter Whey Mug Cake
Prep time: 5 min
Total time: 5 min
Yield: 1 serving
Ingredients: 20 g Rolled oats; 1 tbsp (15 g) Peanut butter; 20 g (two thirds of a scoop) Whey protein isolate; 1 white, about 33 g Egg white; 40 ml Skimmed milk; Half a teaspoon Baking powder; To taste Granulated sweetener

Oats, whey and a spoon of peanut butter, cooked in a mug. Tastes of the peanut butter, as it should. 27 g of protein.

Calories: 271kcal
Protein: 27g
Fat: 9g
Carbs: 17g

Per serving, makes 1. 5 minutes of work. Published 8 September 2026.

Allergens

Gluten
Milk
Eggs
Peanuts

Oats count as a gluten cereal under UK labelling and ordinary oats are milled alongside wheat. Certified gluten-free oats are a separate ingredient here.
Most whey powders contain soya lecithin, which counts as soya. Check the tub.

Flags follow UK labelling rules and come from the ingredients as listed, not from any particular brand. Check the packet before cooking for somebody with an allergy.

Ingredients

Rolled oats20 g
Dry weight.
Peanut butter1 tbsp (15 g)
The kind that is peanuts and salt. Sweetened spreads carry more carbohydrate.
Whey protein isolate20 g (two thirds of a scoop)
Values for an unflavoured or lightly flavoured isolate. A concentrate or a blend carries more fat and carbohydrate at the same scoop.
Egg white1 white, about 33 g
Skimmed milk40 ml
Baking powderHalf a teaspoon
Granulated sweetenerTo taste

Method

Soften the peanut butter in a large mug in the microwave for ten seconds, then beat in the egg white and milk.
Stir in the oats, whey, baking powder and sweetener until there are no lumps of powder.
Microwave on full power for eighty to ninety seconds until the top is set. Let it stand for a minute; the centre finishes cooking as it sits.

Worth knowing

One level tablespoon of peanut butter is the whole of the fat here. A heaped one is nearly double, and the difference shows in the figure.
Two thirds of a scoop of whey rather than a full one keeps the cake from going rubbery. More whey means a firmer, drier result.

Other snack recipes that share ingredients with this one, or every snack under 300 calories a serving.

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Macros are calculated from the weights listed above using standard food composition values, and will shift with your own brands and measuring. Weigh what you can. This is a recipe, not dietary advice. The full health disclaimer is below.