Crack Pie with Speculoos

Ingredients

• 2/3 cup plus 1 tablespoon all-purpose flour
• 1/8 teaspoon baking powder
• 1/8 teaspoon baking soda
• 1/4 teaspoon salt
• 1/2 cup (1 stick) softened butter
• 1/3 cup light brown sugar
• 3 tablespoons sugar
• 1 egg
• 1 cup rolled oats
• Crumbled oat cookie
• 1/4 cup butter (1/2 stick), plus a possible 2 extra tablespoons
• 1 1/2 tablespoons brown sugar
• 1/8 teaspoon salt
• 1 1/2 cups sugar
• 3/4 cup plus 3 tablespoons light brown sugar
• 1/3 cup Nonfat Dry Milk
• 2 tablespoons softened butter
• 1 cup Speculoos or Trader Joe's Cookie Butter
• 1/2 cup heavy cream
• 1 teaspoon vanilla
• 8 egg yolks
• Powdered sugar, for garnish