Choose a microwave-safe mug or ramekin (around 6–8 ounces in size) to ensure the cake cooks evenly. Lightly grease the inside with butter or non-stick spray to prevent sticking. This is essential for that perfect molten center!

In your chosen mug or ramekin, melt the butter in the microwave for about 20-30 seconds. Keep an eye on it to avoid overheating.

Once the butter has melted, add the sugar, cocoa powder, flour, baking powder, and salt to the mug. Stir well with a spoon or a small whisk until the ingredients are fully combined. You should have a smooth, thick batter.

Stir in the milk and vanilla extract to bring everything together. You’ll notice the batter becoming a bit smoother and lighter in texture, which is exactly what you want.

Gently press a piece of dark chocolate into the center of the batter. This will melt into a gooey, molten center as the cake cooks—your lava effect!

Microwave your lava cake on high for about 1 minute and 10 seconds, though microwave times may vary. Start checking at around 1 minute to see if the cake has risen and formed a soft, slightly wet center. You want the outer edges to be set, but the center should still look a little gooey. If it needs more time, continue to microwave in 10-second increments.

Once done, let the cake sit for 1–2 minutes. This gives the lava center time to set a little and cool down enough to avoid burning your tongue when you dig in.