Mix streusel ingredients: In a medium bowl, whisk together the brown sugar, flour, pumpkin pie spice, cinnamon, and salt.
1 cup dark brown sugar, 1 cup all-purpose flour, 2 tsp. pumpkin pie spice, 1/2 tsp. ground cinnamon, 1/4 tsp. kosher salt, 1/2 cup unsalted butter
Finish making streusel: Add the cold cubed butter and cut it into the dry ingredients using a pastry cutter, two forks, or your fingertips until the mixture forms pea-sized crumbles with a few larger chunks remaining. Don't overwork the mixture. you want plenty of buttery clumps. Place the streusel in the refrigerator while you prepare the pumpkin bread batter.
Prepare the pumpkin bread: You’ll need two 8.5 x 4.5 inch loaf pans. Follow my recipe for Best Pumpkin Bread. You’ll stop at Step 6 (after pouring the batter into the pans). You want to skip the sugar sprinkle on top since for this recipe, we’re adding the streusel. Best Pumpkin Bread recipe
Add streusel: Remove the chilled streusel from the refrigerator and generously sprinkle it over both loaves, gently pressing a few of the larger crumbles into the batter so they stay in place during baking.
Bake: Bake for 60-70 minutes, or until a toothpick inserted into the center comes out clean or with just a few moist crumbs attached. Start Timer If the streusel begins browning too quickly, loosely tent the loaves with foil during the final 20 minutes of baking.
Cool: Allow the bread to cool in the pans for about 15 minutes before transferring to a wire rack to cool completely. Start Timer
Make glaze: Whisk together the powdered sugar, melted butter, vanilla, and salt. Add 2 teaspoons milk and whisk really well until smooth. If needed, add additional milk, 1 teaspoon at a time, until the glaze falls from the whisk in a ribbon. If it becomes too thin, whisk in a little more powdered sugar. If your icing breaks or separates, your butter may have been too hot. Drizzle over the completely cooled loaves. Allow the glaze to set for about 10-15 minutes before slicing and serving (if you can wait!) and enjoy! Start Timer
1 cup powdered sugar, 1 Tbsp. unsalted butter, 1/2 tsp. vanilla extract, pinch of salt, 1-2 Tbsp. milk