Blend 1 cup butter with 1 1/2 cups sugar until light and fluffy.
Add the 2 eggs and mix well.
Sift together flour, baking powder, salt and nutmeg.
Add these dry ingredients to the butter and sugar mixture.
Blend in the milk and mix together thoroughly.
Place 1 TBSP of batter in each muffin cup and top with 1 TBSP of cinnamon filling. Using back of spoon, press cinnamon filling lightly into batter, then top with remaining batter. Sprinkle streusel topping evenly over batter.
Bake at 350 until muffins are light golden brown brown and tooth pick inserted into center comes out with a few dry crumbs (about 20-25 minutes) Cool muffins in tin for 30 minutes, then carefully transfer to rack to cool.