St. Louis Gooey Butter Cake (from Smitten Kitchen):
For the cake:
3 tbsp milk at room temperature
1 3/4 tsp active dry yeast
6tbsp unsalted butter at room temperature
3 tbsp sugar
1 tsp kosher salt
1 3/4 cups all-purpose flour
For the topping:3 tbsp plus 1 tsp light corn syrup
2 1/2 tsp vanilla extract
1 1/2 sticks unsalted butter, at room temperature
1 1/2 cups sugar
1/2 tsp kosher salt
1 cup plus 3 tbsp all-purpose flour
Confectioner's sugar to sprinkle on top
To make the cake dough:
In a small bowl, mix milk with 2 tbsp warm water. Add yeast and whisk gently until it dissolves. Mixture will foam slightly.
Using an electric mixer with paddle attachment, cream butter, sugar, and salt. Scrape down sides of bowl and beat in the egg. Alternately add the flour and the milk mixture, scraping down the sides of the bowl between each addition. Switch to a dough hook and beat dough on medium speed until it forms a smooth dough, about 5 minutes. It will still be sticky.
Grease a 9x13 ceramic baking dish and spread the dough, stretching it evenly. Cover the pan with a sheet of plastic wrap and put it in a warm place, allowing it to rise until doubled, about 2 1/2 hours.
To make the topping:
Preheat oven to 350 degrees. In a small bowl, whisk corn syrup with 2 tbsp water and the vanilla. In your electric mixer fitted with the paddle attachment, cream butter, sugar, and salt until light and fluffy, 5-7 minutes. Scrape down the sides of the bowl and add the egg. Beat until well mixed. Alternately add flour and corn syrup mixture, scraping down sides of the bowl between additions.
Spoon the topping evenly over risen cake, and spread evenly with an offset spatula. Bake 30-40 minutes, watching very carefully at the 30 minute mark. Cake will have a barely golden top when done, and will rise and fall in waves. The center of the cake should still be quite liquidy, and will set up while the cake is cooling. I have made it twice, and the second time I overcooked it by a few minutes, and it made a very big difference, so don't let it go too long. After cooling, sprinkle with confectioner's sugar. Serve at room temperature.