Preheat & Line Pan: Preheat your oven to 425°F (218°C). Line a standard 12-cup muffin tin with paper or parchment tulip liners. (Starting at high heat creates that signature bakery-style dome!).

Make the Cinnamon Streusel: In a small bowl, whisk together 1/2 cup flour, 1/3 cup brown sugar, 1 tsp cinnamon, and chopped pecans (if using). Add 1/4 cup cold cubed butter and cut in using a pastry blender or your fingertips until coarse, pea-sized crumbs form. Place in refrigerator to stay cold while preparing batter.

Whisk Dry Ingredients: In a large bowl, whisk together 1 3/4 cups flour, baking soda, baking powder, pumpkin pie spice, cinnamon, and fine sea salt until well aerated and combined.

Whisk Wet Ingredients: In a separate medium bowl, whisk together pumpkin puree, granulated sugar, brown sugar, melted butter, eggs, milk, and vanilla extract until glossy, smooth, and fully emulsified.

Gently Fold Batter: Pour the wet mixture into the dry flour mixture. Using a rubber spatula, fold gently just until no dry pockets of flour remain. Avoid overmixing to ensure a tender, fluffy crumb.

Fill Muffin Cups & Mound Streusel: Divide batter evenly among the 12 muffin liners, filling each cup about 3/4 to 7/8 full. Spoon the chilled cinnamon streusel generously over each muffin, gently pressing crumbs into the surface so they adhere during baking.

The Bakery Rise Bake: Bake at 425°F (218°C) for 5 minutes. Then, keeping the oven door closed, lower the oven temperature to 350°F (175°C) and continue baking for 15 to 17 minutes, until the tops spring back when gently touched and a toothpick inserted into the center comes out clean.

Cool & Glaze: Cool in the muffin pan for 5 minutes, then transfer muffins to a wire cooling rack. If desired, whisk powdered sugar, milk, and vanilla, and drizzle over the warm muffins before serving!