In a small bowl, mix the brown sugar, flour, and cinnamon. Cut the butter using a fork or your fingertips until crumbly and sandy in texture. Refrigerate or freeze until ready to use
1/3 cup brown sugar, 1/2 cup all purpose flour, 1/4 tsp salt, 1 tsp cinnamon, 4 tbsp butter
Preheat oven to 425°F . Line a 12-cup muffin pan with paper liners only in every other cup (place six liners total, leaving one empty hole beside each filled one). Lightly spray the top of the pan (around the filled cups) with nonstick spray as needed.
In a medium bowl, whisk together flour, baking soda, baking powder, salt, cinnamon, pumpkin pie spice, and nutmeg.
2 cups all-purpose flour, 1 tsp baking soda, 2 tsp baking powder, ½ tsp salt, 2 tsp cinnamon, 1 tsp pumpkin pie spice, ½ tsp ground nutmeg
In a large bowl, whisk together brown sugar, granulated sugar, oil, eggs, pumpkin purée, milk, and vanilla. Mix until completely smooth and combined.
3/4 cup brown sugar, ½ cup granulated sugar, ¾ cup neutral oil, 2 large eggs, 1 cup pure pumpkin purée, ¼ cup milk, 1 tsp vanilla extract
Add dry ingredients to wet and fold gently with a spatula just until no dry streaks remain (do not overmix).
Divide the batter evenly among the six prepared liners, filling each almost to the top (this helps form tall domes). Sprinkle a generous amount of chilled streusel in the center of each muffin, keeping the topping away from the very edges to prevent over-browning.
Bake at 425°F for 5 minutes, then (without opening the oven) reduce temperature to 350°F and continue baking for 14-16 more minutes, or until a toothpick comes out clean. The initial high heat helps them rise tall and round.
Let muffins cool in the pan for 5 minutes, then transfer to a rack. Once completely cool, sift powdered sugar over the tops for that classic Panera look.
Powdered sugar for dusting