For the muffins:

1. Cream the butter and sweetener together until smooth.
2. Add the eggs, beating well after each.
3. Add the vanilla extract and mix well.
4. Combine the almond flour, coconut flour, salt, baking powder, and xanthan gum (or psyllium husk powder) in a medium bowl.
5. Add to the wet ingredients and mix well.
6. Pour in the almond milk and blend until smooth.
7. Stir in blueberries.
8. Divide the batter between 8 greased muffin tins – with or without paper liners.

For the streusel topping:

1. Melt the butter and add the rest of the streusel ingredients.
2. Stir until a dough forms.
3. Using your fingers, crumble the streusel over the tops of the muffin batter.
4. Bake the muffins at 375 degrees for 20 minutes, or until a toothpick inserted in the center comes out clean.
5. Remove from the oven and cool.

For the cream cheese icing:

1. Whip the softened cream cheese with the sweetener and lemon juice until smooth.
2. Spoon into a ziploc bag and cut off the very tip with scissors.
3. Squeeze the icing over the cooled muffins and serve.