In a mixing bowl, beat together softened cream cheese, one egg yolk, and powdered sugar until smooth. Scoop mixture into dollops and freeze for about 30 minutes.

In a medium bowl, combine flour, cold cubed butter, and sugar for crumb topping. Mix until it resembles coarse crumbs.

In a large bowl, cream together softened butter, oil, and brown sugar until light and fluffy. Add egg whites gradually until smooth.

In a separate bowl, whisk together cake flour, baking powder, cocoa powder, baking soda, and salt.

Gradually add dry ingredients to wet mixture, alternating with buttermilk. Stir gently until combined.

In another bowl, whip heavy cream until soft peaks. Fold into muffin batter gently to maintain lightness.

Preheat oven to 425°F. Grease muffin pan. Fill each cup halfway with batter, place a frozen dollop of cream cheese in center, then top with remaining batter.

Sprinkle crumb topping over each muffin and press down slightly.

Bake at 425°F for 6 minutes, then reduce temperature to 350°F and bake for 18-22 minutes until a toothpick comes out with moist crumbs.

Allow muffins to cool in the tin for about 10 minutes then transfer to a wire rack to cool completely.