Ingredients

For the batter:
• ½ cup (1 stick / 115g) unsalted butter, softened
• ¾ cup (150g) packed brown sugar
• 1 large egg
• 1 tsp vanilla extract
• ¾ cup (95g) all-purpose flour
• ½ tsp baking powder
• Pinch of salt
• ¾ cup (180ml) whole milk

For the sauce base (goes on top before baking):
• ¾ cup (150g) packed brown sugar
• 2 tbsp all-purpose flour
• 1½ cups (360ml) hot water
• Optional: 1–2 tbsp bourbon or rum for depth

Instructions

Preheat oven to 350°F (175°C). Grease a 2-quart baking dish (or 6 ramekins).
Batter: In a bowl, beat butter and brown sugar until fluffy. Add egg and vanilla; mix well.
Whisk flour, baking powder, and salt. Alternate adding dry ingredients and milk to batter, beginning and ending with flour. Spread evenly in dish.
Sauce base: In a separate bowl, whisk brown sugar and flour. Sprinkle evenly over batter.
Carefully pour hot water (and bourbon, if using) over the back of a spoon onto the surface—do not stir!
Bake 35–40 minutes until top is puffed and golden, and sauce bubbles around edges.
Let rest 5–10 minutes before serving. The sauce will settle beneath the cake layer.
Serve warm in bowls with vanilla ice cream or whipped cream.