Begin by combining all the dry ingredients in a small bowl. Mix together 4 tablespoons of all-purpose flour, 3-4 tablespoons of sugar, 1 tablespoon of unsweetened cocoa powder, 1/4 teaspoon of baking powder, and 1/8 teaspoon of salt until well blended. In a separate small container, whisk together 1 beaten egg, 3 tablespoons of milk, and 1 tablespoon of vegetable oil. Pour the wet ingredients into the dry mixture and stir until you have a smooth batter with no lumps. This step is essential for achieving an evenly textured cake.
Transfer the batter into a regular-sized coffee mug, filling it about halfway. This allows room for the cake to rise as it cooks. Drop either 2 caramels or 2 tablespoons of chocolate chips into the center of the batter. These ingredients will create a delightful surprise in the middle of your cake—caramels will produce a gooey, melted center while chocolate chips will soften and blend into the cake.
Place the mug in the microwave and cook on high power for one and a half minutes. Check the cake for doneness by inserting a toothpick into the center; it should come out mostly clean with just a few moist crumbs. If the cake still appears wet or underdone, microwave for an additional 30 seconds and check again. Once cooked through, allow the mug to cool for a minute or two before enjoying your freshly made single-serving chocolate cake.
