In an over sized mug whisk together the dry ingredients.
Add the wet ingredients to the mug and mix until you have a smooth but thick batter.
Place the chocolate pieces on top of the batter, pressing lightly. Add 1 tablespoon of hot water on top.
Microwave at high heat for 1-2 minutes. The exact time will depend on your microwave.
The cake is done when the edges are slightly set but the middle is still a bit wet. Do not over cook.
Let the cake cool for about 10 minutes. The cake will sink slightly.
Serve with whipped cream and top with Hershey's chocolate syrup.
Can room temperature milk actually change the texture of a small single-serving cake? Using dairy straight from the refrigerator drops the temperature of melted butter upon contact, causing the fat to solidify into tiny pellets rather than emulsion. This temperature shock prevents trapped air from expanding uniformly, yielding a dense, rubbery crumb instead of a light sponge. Whisking dry components like all-purpose flour, baking powder, and unsweetened cocoa powder thoroughly before adding liquids guarantees even leavening distribution. Incorporating half an egg requires beating a whole egg in a separate bowl and measuring out roughly two tablespoons, a precision step that prevents excess moisture from turning the batter into soup. Swapping all-purpose flour for cake flour alters the protein structure entirely, removing the gluten network needed to support the rising agents during rapid microwave expansion. Granulated white sugar paired with light brown sugar balances sweetness while molasses adds necessary moisture retention, preventing the flour from drying out under high wattage. Pressing solid chocolate pieces onto the surface before cooking allows gravity to pull molten cocoa downward, creating pockets of fudge as the starch sets. Overcooking remains the primary pitfall in single-serving baking, as microwave radiation continues to cook the center even after the machine stops running. Removing the mug while the middle still glistened ensures residual heat finishes the center without over-baking the perimeter.