• Preheat the oven to 425°F/220°C. Spray a muffin tin with nonstick or line it with 12 paper muffin liners.

Streusel and pecans

• In a small bowl, combine melted butter, granulated sugar, cinnamon, and all-purpose flour. Use a fork to combine this flour mixture into a coarse crumb, then set it aside.
• Heat a dry, non-stick pan over medium heat. Once the pan is hot, add the pecans and spread them in a single layer.
• Stir the pecans frequently to prevent burning, and toast them for 3-5 minutes or until they are fragrant.
• Remove the pecans from the heat and transfer them to a bowl to cool down.
• After cooling, finely chop ¼ of the toasted pecans and add them to the streusel.
• Roughly chop the chop the remaining pecans and set them aside.

Muffin batter

• In a small bowl, combine flour, spices, salt, baking soda, and salt and whisk. Set aside.
• In a large bowl, add the sugar, vegetable oil, pumpkin purée, eggs, vanilla, and milk. Whisk it all together.
• Add the dry ingredients to the pumpkin mixture and mix them together with a rubber spatula until combined. Don't over-mix it. 
• Fold through the remaining chopped pecans. 
• Divide pumpkin muffin batter evenly over 12 muffin cups; they will be very full. You could also make 14 smaller muffins.
• Generously pile the buttery pecan streusel mixture on each muffin. Gently press it on top to keep it in place.
• Bake the muffins at 425°F/220°C for 5 minutes, then turn the oven down to 350°F/180°C and continue baking for another 18 minutes or until the tops of the muffins spring back when lightly pressed.
• Remove them from the oven and let the muffins cool in the pan for 10 minutes before removing the warm muffins and placing them on a wire rack to cool to room temperature.