Preheat oven to 400ºF. Spray 6 cups of a muffin pan with nonstick cooking spray and set aside.Combine eggs, sour cream, and melted butter and whip until fully combined and lumps are gone. Set aside.Combine all dry ingredients until fully incorporated.Add wet ingredients to dry and mix just until combined.Mix in cheeses.Spoon batter evenly into the six greased muffin cups. Bake for 10-12 minutes, or until tops have risen and have started to brown.Place hot muffin pan on a cooling rack until the muffins are cool enough to handle. Serve warm with butter, or transfer muffins to the cooling rack to finish cooling. Keep muffins in an airtight bag for storage.