Preheat the oven to 350° F. Line 24 mini muffin pan wells with paper liners and set aside. In a bowl whisk together the flour, baking powder, salt, and pumpkin pie spice. Set aside.
In another mixing bowl, whisk together the pumpkin, eggs, oil, brown sugar, and vanilla until smooth. Sprinkle the flour mixture over the wet mixture and fold until just combined. Spoon the batter into the muffin liners, about 3/4 full.
Make the topping if you want to include it: combine the flour, sugar, and cinnamon in a bowl. Cut in the butter and use a fork or pastry fork to mix until crumbly.
Spoon the streusel evenly over each portion of the muffin batter. Bake for about 9-11 minutes or until middle springs back when you touch it gently.
Do NOT overbake these. Keep a close eye at the last minute or so and as soon as the middle springs back when touched gently take the pan out and remove muffins on to a cooling rack.