Preheat the oven to 350°F. Line a muffin tin with muffin/cupcake liners.
Prepare the streusel by combining the all purpose flour, brown sugar, chopped pecans, pumpkin pie spice, and softened butter in a mixing bowl. Use a large spoon, silicone spatula, or your hands to mix the mixture until it's crumbly. Set aside.
In a large mixing bowl, beat the softened butter, granulated sugar, and brown sugar until it is pale and fluffy, after a few minutes.
Add the pumpkin puree, egg, vanilla, and milk. Mix on low speed until it’s well combined, after about 1 minute.
Add the all purpose flour, baking powder, baking soda, pumpkin pie spice, and salt. Gently mix with a large spoon or silicone spatula until you no longer see dry pockets of flour. Scrape the sides and bottom of the bowl to ensure everything is well mixed.
Use a cookie scoop or a large spoon to drop muffin batter into each muffin cup to fill it nearly to the top. Sprinkle the pecan streusel topping on top.
Bake the muffins for 18 to 22 minutes, until a toothpick inserted into the center of the muffins comes out without any wet batter stuck to it. Enjoy!!