This peanut butter cake in a mug has been my indulgent, single-serving treat on evenings when I want something warm, sweet, and impossibly easy. I first stumbled on the idea during a late-night craving when I had a jar of peanut butter, a few basics in the pantry, and a 14-ounce mug close at hand. Within two minutes I had a batter, and in less than three I had a soft, tender cake that felt like a tiny celebration. The texture is moist and slightly dense from the peanut butter, with buttery notes and a caramelized edge where the batter meets the mug. It tastes like a warm peanut butter cookie turned into a cake and it makes the whole kitchen smell wonderfully familiar.

I make this when I need a single portion without committing to a whole cake, and it has become my go-to for sudden dessert urges and cozy movie nights. The recipe is forgiving, requires no electric mixer, and uses tools you already own. Because it uses self-rising flour and just the right balance of sugar and butter, the crumb comes out soft and tender while the peanut butter gives that signature nutty depth. I love how a spoonful of extra peanut butter on top melts into a silky glaze while the cake cools, making each bite richer and more luscious.

Ingredients

• Self-rising flour: Use 4 tablespoons of self-rising flour. If unavailable, make your own by combining 4 tablespoons all-purpose flour with 1/8 teaspoon baking powder and a pinch of salt. Choose unbleached all-purpose for the best texture.
• Granulated sugar: 3 tablespoons granulated sugar provide the right balance of sweetness and structure. For a slightly deeper flavor, you can substitute 1 tablespoon with brown sugar, but granulated gives the characteristic tender crumb.
• Creamy peanut butter: 4 tablespoons creamy peanut butter folded into the batter create the cake's nutty backbone. Use a familiar brand you like; sodium content and sweetness vary by brand and will affect final taste slightly.
• Optional garnish: 1 tablespoon extra creamy peanut butter to melt on top for a glossy finish and extra richness.
• Whole milk: 3 tablespoons whole milk adds tenderness and helps the batter come together. For a lighter bite, use 2% but expect a minimally drier crumb.
• Salted sweet cream butter: 3 tablespoons melted butter contribute richness and a soft crumb. Salted butter enhances flavor; if using unsalted, add a pinch of salt to the batter.
• Pure vanilla extract: 1/2 teaspoon to round out and elevate the peanut butter flavor with a warm, aromatic note.

Instructions

Combine dry ingredients: Into a 14-ounce microwave-safe mug, add 4 tablespoons self-rising flour and 3 tablespoons granulated sugar. Stir thoroughly with a fork to remove lumps and evenly distribute the sugar. This ensures even rise and prevents pockets of unmixed flour when microwaving. Add wet ingredients: Spoon in 4 tablespoons creamy peanut butter, then pour 3 tablespoons whole milk and 3 tablespoons melted salted butter. Add 1/2 teaspoon pure vanilla extract. Use the fork or a small whisk to stir until the batter is smooth and glossy, scraping down the sides. The peanut butter may be slightly viscous; keep stirring to fully incorporate. Microwave to cook: Place the mug in the center of the microwave and cook on high for 1 minute 30 seconds to 1 minute 45 seconds. Microwave power varies; start with 1 minute 30 seconds and check. The cake should be set on top and spring back lightly when touched. A toothpick inserted in the center may come out with a few moist crumbs but not wet batter. Cool and finish: Let the cake rest in the mug for 2 to 3 minutes to finish cooking and set. If using the optional tablespoon of peanut butter, dollop it on top while the cake is warm so it melts into a silky topping. For a smoother finish, let the peanut butter sit for 30 seconds and gently spread with the back of a spoon.

Storage Tips

This cake is best served immediately for optimal texture and warmth. If you must store leftovers, transfer the cooled cake to an airtight container and refrigerate for up to 2 days; note the crumb will be slightly firmer. Reheat in 15-second bursts in the microwave until warm. Do not freeze the cake in the mug; freezing changes the crumb and can create a gummy texture. For make-ahead convenience, mix dry ingredients and store in a small jar, then add wet ingredients and microwave when ready.

Ingredient Substitutions

To make this dairy-free, use a plant-based butter alternative and a non-dairy milk such as oat or soy. For a gluten-free version, use a 1-to-1 gluten-free flour blend that contains baking powder or substitute with the recommended homemade self-rising mix using gluten-free flour plus baking powder. Swap peanut butter for almond butter or sunflower seed butter to avoid peanut allergies; sunflower butter will keep the flavor profile close but slightly earthier. If you prefer a less rich cake, reduce the butter to 2 tablespoons and add an extra tablespoon of milk to maintain moisture.

Serving Suggestions

Serve warm straight from the mug with a spoonful of creamy peanut butter on top, a drizzle of chocolate sauce, or a small scoop of vanilla ice cream for a classic contrast of hot and cold. Garnish with chopped roasted peanuts for texture and a sprinkle of flaky sea salt to balance the sweetness. For a breakfast twist, top with sliced banana and a dusting of cinnamon and enjoy with a cup of coffee. The mug presentation is perfect for a cozy solo treat or as part of a casual dessert spread.

Cultural Background

Single-serve microwave cakes have roots in simple, resourceful cooking where convenience meets comfort. Mug cakes became popular as a quick method to satisfy dessert urges without baking an entire cake. This peanut butter variation combines American pantry staples, with peanut butter itself being a staple in North American cuisine since the late 19th century. The combination of peanut butter and butter evokes the classic peanut-butter-cookie flavors adapted to a fast, microwave method.

Seasonal Adaptations

In cooler months, add a pinch of ground cinnamon and 1/8 teaspoon nutmeg for a warm spice profile. For summer, top the warm cake with fresh berries or a berry compote for brightness. Around holidays, fold in 1 tablespoon mini chocolate chips or swirl in a teaspoon of pumpkin butter for festive flair. Small seasonal swaps will shift the cake’s character without changing the quick preparation method.

Meal Prep Tips

For batch prepping, measure dry mixes into small jars for 2 to 4 single-servings, labeling each jar. When ready, add wet ingredients directly to the jar or combine in a mug and microwave. Use microwave-safe mugs of the same size to ensure consistent cooking times. Portion the optional peanut butter in small ramekins or pre-measure tablespoons to speed assembly. This method makes it easy to serve multiple people quickly with minimal fuss.

There’s something gently satisfying about this tiny cake: a humble combination of pantry staples transformed into a warm, comforting treat in minutes. Make it yours with small tweaks, and savor the joyful simplicity of a dessert that never requires a full oven.