1. Preheat oven to 425*. Line a muffin tin with baking cups.
2. In a large bowl cream butter and oil. Add sugars mixing well. Add eggs one at a time mixing well after each addition.
3. In a medium bowl, combine dry ingredients and whisk together. Add half of the flour mixture to the butter, stirring until just combined. Stir in the milk. Add remaining flour mixture and stir until just combined.
4. Fill cups 3/4 full. Bake for 15-17 minutes or until toothpick test is clear. Move to wire rack to cool slightly.
5. Dip tops in the melted butter then into the cinnamon sugar mix. Cool completely before coring and filling.
Vanilla pastry cream:
1. Dissolve cornstarch in 1/4 cup milk in a small bowl. Add egg and yolks one at a time mixing well after each addition.
2. Bring remaining milk and the sugar to a boil whisking constantly.
3. While whisking the egg mixture, temper egg with milk. Once tempered, add egg mixture to milk slowly while whisking the milk mixture. Bring to a boil, whisking constantly.
4. Once thickened, remove from heat. Stir in butter and vanilla. Place plastic wrap on top of the cream to prevent skin from forming. Cool to room temp. before filling muffins.