Preheat the oven to 400°F. Grease the top of a standard 12-cup muffin tin and line 6 of the cups, staggering them.
Whisk together the flour, salt, baking powder and baking soda.
Make the muffin batter. In a large mixing bowl, whisk together the butter and sugar.
Mix the dry ingredients into the butter and sugar until the mixture is crumbly. Reserve 1/4 cup of the crumbles for the topping.
Add the egg and mash it into the butter and sugar with a rubber spatula, trying to break up the crumbles a bit. Whisk in the pumpkin purée, milk, vegetable oil, vanilla extract, cinnamon, nutmeg, ginger and espresso powder. Mix until combined (it’s okay if there are a few lumps).
For the filling, combine the dark brown sugar, espresso powder, cinnamon and salt.
For each muffin, fill the lined cup with a heaping tablespoon of batter, then cover that with the filling mixture, about 1 1/2 teaspoons. Repeat. Then, add a final heaping tablespoon of batter and sprinkle some reserved streusel on top.
Bake the muffins on the middle rack for 11 minutes, then turn the oven down to 350°F, rotate the tin, and bake for about 12 more minutes or until the muffin edges are golden brown, and the tops spring back when lightly pressed in the middle.
Allow the muffins to cool completely in their tin.
