Crack Pie - Hey Recipe

Ingredients

• 9 tablespoons unsalted butter (room temperature, divided)
• 5 1/2 tablespoons light brown sugar (packed, divided)
• 2 tablespoons granulated sugar
• 1 large egg (room temperature)
• 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 salt
• 3/4 cup granulated sugar
• 1/2 cup light brown sugar (packed)
• 1 tablespoon nonfat dry milk powder
• 1/2 cup unsalted butter (melted and cooled slightly)
• 6 1/2 tablespoons heavy whipping cream
• 4 large egg yolks
• 1 teaspoon vanilla extract
• confectioners' sugar (to taste, for serving)