Pumpkin Streusel Muffins

1/4 c margarine or butter, softened
1/2 c sugar
1/4 c brown sugar
2/3 c pumpkin
1/2 c buttermilk
2 eggs
2 c flour
1 tsp baking soda
2 tsp baking powder
1 tsp pumpkin pie spice (I used cinnamon, nutmeg, and ginger b/c that's what I had)

Streusel Topping:
1/3 c flour
3 Tbsp brown sugar
2 Tbsp cold butter or margarine

For muffins:
Cream together margarine and sugars. Add all remaining ingredients and mix together. Pour into muffin tins. In a separate bowl, cut together streusel ingredients and sprinkle over muffin batter. Bake in a 375 degree oven for 20-25 minutes. Makes one dozen muffins.