Prep the pan: Heat oven to 375°F (190°C).
Line a 12-cup muffin tin with liners or grease well.
Make the streusel: In a bowl, mix flour, sugars, cinnamon, and salt. Cut in the cold butter with a fork or fingers until clumpy. Chill while you make the batter.
Whisk dry ingredients: In a large bowl, combine flour, baking soda, baking powder, salt, cinnamon, nutmeg, and ginger.
Whisk wet ingredients: In another bowl, whisk brown sugar, granulated sugar, eggs, pumpkin, oil, milk, and vanilla until smooth.
Combine: Pour wet into dry.
Fold gently with a spatula until just combined. Do not overmix; a few small lumps are fine.
Fill the cups: Divide batter evenly among the muffin cups, filling each about 3/4 full.
Top with streusel: Sprinkle a generous mound of streusel on each muffin, pressing lightly so it adheres.
Bake: Bake 18–22 minutes, until a toothpick comes out clean or with a few moist crumbs, and tops are golden.
Cool: Let muffins cool in the pan 5 minutes, then transfer to a rack. Serve warm or at room temp.