Preheat oven to 350 degrees. Line muffin pans with paper muffin liners.

In a large bowl, whisk together flour, sugar, baking powder, salt and spices. In a separate bowl, beat together the pumpkin puree, oil, eggs, vanilla and milk. Stir the pumpkin mixture into the flour mixture until just blended.

To make the streusel, combine flour, brown sugar and cinnamon in a small bowl. Cut in butter until mixture resembles coarse crumbs.

Fill muffin cups 2/3 full with batter. Sprinkle streusel generously over batter. Bake muffins for 17-23 minutes, or until a toothpick inserted in the center comes out clean.