Crack Pie

Name: Crack Pie
Cuisine: American
Ingredients: Nonstick vegetable oil spray; 9 tablespoons (1 stick plus 1 tablespoon) unsalted butter, room temperature, divided; 5 1/2 tablespoons (packed) golden brown sugar, divided; 2 tablespoons sugar; 1 large egg; 3/4 cup plus 2 tablespoons old-fashioned oats; 1/2 cup all purpose flour; 1/8 teaspoon baking powder; 1/8 teaspoon baking soda; 1/4 teaspoon (generous) salt; 3/4 cup sugar; 1/2 cup (packed) golden brown sugar; 1 tablespoon nonfat dry milk powder; 1/4 teaspoon salt; 1/2 cup (1 stick) unsalted butter, melted, cooled slightly; 6 1/2 tablespoons heavy whipping cream; 4 large egg yolks; 1 teaspoon vanilla extract; Powdered sugar (for dusting)