Whisk Wet Ingredients: In a small, non-stick cooking pot, whisk together the egg and sugar until frothy. Stir in the milk and oil.

Add Dry Ingredients: Add the flour, cocoa powder, baking powder, and vanilla directly into the pot. Whisk until the batter is smooth and no flour clumps remain.

Prepare for Cooking: Clean the inner edges of the pot with a spatula. Place a tight-fitting lid on the pot.

Stovetop "Bake": Place the pot on the smallest burner over low-to-medium heat.

The "No-Peek" Rule: Cook for 25 minutes. Do not open the lid for the first 20 minutes to ensure the steam stays trapped for a moist rise.

Check Doneness: After 25 minutes, insert a toothpick into the center. If it comes out clean, remove the pot from the heat.

Make the Sauce: While the cake cools slightly, whisk the sauce ingredients (milk, cocoa, and sugar) in a separate bowl until the sugar is fully dissolved.

Soak and Decorate: Poke several small holes in the warm cake with a skewer. Pour the chocolate sauce over the top. Let it sit for a few minutes to absorb.

Celebrate: Decorate with sprinkles, chocolate letters, or candles directly in the pot and serve.