Hot Fudge Sundae Cake

I have never had any luck making the gooey, molten chocolate cakes. It never does what it's supposed to do for me. But since I'm absolutely giddy about making dessert in the crock pot, I think I might give this one a whirl...{Via the Rach.}

Cooking spray
1 cup flour
1/2 cup plus 1/3 cup granulated sugar
1/4 cup plus 5 tablespoons unsweetened cocoa powder
2 teaspoons baking powder
1/4 teaspoon salt
1/2 cup milk
2 tablespoons mild olive oil
1 1/2 teaspoons pure vanilla extract
2/3 cup packed light brown sugar
1/2 teaspoon espresso powder
1 1/2 cups boiling water
1 cup heavy cream, chilled

1. Spray the slow cooker with cooking spray. In a bowl, mix the flour, 1/2 cup granulated sugar, 2 tablespoons cocoa, the baking powder and salt. Stir in the milk, olive oil and vanilla. Scrape the batter into the slow cooker and smooth the top. In a small bowl, combine the brown sugar, 1/4 cup cocoa powder and the espresso powder. Whisk in the boiling water. Pour the mixture over the batter.
2. Cover and cook on high until a toothpick inserted into the center comes out clean, about 1 hour. Turn off the slow cooker, remove the lid and let the cake cool, 30 minutes.
3. Meanwhile, in a small bowl, whisk together the remaining 1/3 cup granulated sugar and 3 tablespoons cocoa. Whisk in the heavy cream. Cover and refrigerate for 30 minutes. Using a handheld electric mixer, beat the mixture until soft peaks form.
4. Scoop the warm cake and its sauce into bowls. Dollop the cocoa whipped cream on top.