Hot Fudge Spoon Cake

Hot Fudge Spoon Cake
Adapted from Not Your Mother’s Slow Cooker Cookbook, by Beth Hensperger and Julie Kaufmann (Harvard Common Press, 2005).
Simple Solution
Now here is a marvelous idea: a decadent pudding cake that you cook and serve in a slow cooker. A custard-like sauce forms on the bottom with a chocolatey layer of sponge cake on top. You can serve it warm, room temperature, or chilled. Calling all chocolate-lovers: this one sounds absolutely divine.
INGREDIENTS
3/4 cup all-purpose flour
1/4 cup sweet ground chocolate, such as Ghirardelli
1/4 cup sugar
1 1/2 teaspoons baking powder
1/4 teaspoon salt
1/2 cup milk
1/4 cup (1/2 stick) unsalted butter, melted
1 teaspoon vanilla extract
Topping:
1/4 cup sweet cocoa powder, such as Ghirardelli
1/4 cup granulated sugar
1/4 cup firmly packed light brown sugar
1 1/2 cups boiling water
1. Coat the slow cooker with butter-flavor nonstick cooking spray.
2. In a medium-size bowl, whisk together the flour, ground chocolate, sugar, baking powder, and salt. Make a well in the center, add the milk, melted butter, and vanilla, stir the liquid ingredients until well blended, and continue stirring in widening circles, gradually incorporating the dry ingredients, until you have a smooth batter. It will be thick. Spread evenly in the cooker.
3. To make the topping, combine all the ingredients in another medium-size bowl and whisk until smooth. Gently pour over the batter in the cooker, do not stir. Cover and cook on HIGH until puffed and the top layer is set, 2 to 2 1/4 hours.
Serves 4-6.