Stir together flour, next 3 ingredients, and 3/4 cup granulated sugar in a large bowl.
Stir in milk, oil, and vanilla.
Spread batter in a lightly greased 8-inch square pan.
Combine brown sugar, cocoa, and remaining 1/2 cup granulated sugar in a small bowl; sprinkle over batter in pan.
Using a spoon, gently drizzle 1 1/2 cups boiling water over batter, being careful not to disturb layers. (Do not stir.).
Bake at 350° for 45 minutes or until a cake layer forms on top and layer springs back when touched.
Let cool on a wire rack 25 minutes. Serve warm with whipped cream or ice cream.
VARIATION: Chocolate-Cherry Pudding Cake: Thaw 1 (12-oz.) package frozen dark, sweet, pitted cherries; drain. Pat cherries dry with paper towels. Prepare recipe as directed through Step 2, gently sprinkling cherries over batter in pan. Proceed with recipe as directed.
VARIATION: Mocha Pudding Cake: Substitute hot freshly brewed coffee for boiling water. Proceed with recipe as directed.