Preheat oven to 350 F. Line an 8 cup large muffin tin with parchment papers/cups
In a large bowl, whisk together 1 2/3 cups flour, baking soda, baking powder, salt, cinnamon & allspice. In a small bowl, combine pumpkin puree with milk.
In a large bowl, using an electric mixer, beat butter & brown sugar until creamy. Add egg; beat until fluffy.
Alternately add flour & pumpkin mixtures to butter mixture, stirring just until blended. Combine blueberries with 1 Tbsp flour in a small dish. Fold gently into mixture. Spoon batter carefully into prepared muffin cups.
Topping
In a small bowl, combine oats, flour, brown sugar, cinnamon & salt. Using a fork, cut in butter until mixture is crumbly. Add pepitas & combine. Divide evenly over muffin batter.
Baking
Bake for 45 minutes or until a wooden pick inserted in center comes out clean. Remove from oven, cool in pan for a few minutes then remove to a rack to finish cooling. Store muffins in a covered container.
Recipe Notes
If you would prefer smaller muffins, divide batter between 12 paper lined standard muffin cups. Bake for about 30-35 minutes or until a wooden pick inserted in center comes out clean.