Preheat the oven to 375 degrees F.
Place the butter, sour cream and vanilla extract into a stand mixer and mix until smooth.
Whisk the next 7 dry ingredients together then add them to the mixer. Blend on low until incorporated.
Add in 1 egg at a time to the mixer until well absorbed.
Pour in the heavy cream until well absorbed.
Stir in the apple.
Set aside batter while making filling.
Clean your mixer then add the cream cheese, egg yolk, vanilla and stevia. Mix on high until smooth. Set aside.
Use cupcake liners or grease well a 12 capacity muffin pan. Fill each cup half way with batter.
Evenly scoop cream cheese over each muffin. Finish with remaining batter over the cream cheese on each muffin.
Top with a few pieces of apple if desired. Sprinkle some Sukrin Brown Sugar Sub over the top if desired.
Bake for 25 minutes or until a toothpick comes out clean. Best at room temperature or chilled. Keep refrigerated if making ahead for breakfast.