Crack Pie

Name: Crack Pie
Cuisine: American
Ingredients: Nonstick vegetable oil spray; 9 tablespoons (1 stick plus 1 tablespoon) unsalted butter, room temperature, divided; 5½ tablespoons (packed) golden brown sugar, divided; 2 tablespoons sugar; 1 large egg; ¾ cup plus 2 tablespoons old-fashioned oats; ½ cup all purpose flour; ⅛ teaspoon baking powder; ⅛ teaspoon baking soda; ¼ teaspoon (generous) salt; ¾ cup sugar; ½ cup (packed) golden brown sugar; 1 tablespoon nonfat dry milk powder; ¼ teaspoon salt; ½ cup (1 stick) unsalted butter, melted, cooled slightly; 6½ tablespoons heavy whipping cream; 4 large egg yolks; 1 teaspoon vanilla extract; Powdered sugar (for dusting)