Preheat oven to 330ºF. If you don't have that setting go down to 300ºF
Melt butter then let it cool
Mix almond flour, coconut flour, granulated sweetener, apple pie spice, baking powder and salt
Separately combine melted butter, heavy cream, liquid stevia or liquid monk fruit, vanilla extract and 2 eggs
Combine dry and wet ingredients then fold in chopped walnuts
Remove crumble from freezer. Butter will be harder and easier to break apart in small crumbles. Break it apart and add crumble pieces across the muffins. There should be 8 average size muffins
Place in muffin cups and place in oven for 20-30 minutes