PREP: Preheat oven to 350 degrees F. Melt 4 tablespoons butter in the microwave and then set aside to cool to room temperature (We do not want hot butter added to the batter). Generously grease a 9-inch loaf pan with cooking spray and coat with flour, tapping out the excess. Set aside.
DRY INGREDIENTS: In a large bowl, add the flour, baking powder, baking soda, salt, cinnamon, pumpkin pie spice, and nutmeg. Stir to combine.
WET INGREDIENTS: Add the melted (and cooled back to room temperature) butter to a large bowl along with the oil, dark brown sugar, pumpkin, eggs, and vanilla. Stir until smooth.
COMBINE: Combine wet and dry ingredients and mix until just combined. Do not overmix. Use a spatula to scrape the batter into the prepared loaf pan. Smooth the top.
STREUSEL: Melt the butter in the microwave and then let stand at room temperature until cooled (don't add hot butter to the streusel -- it will make it greasy). In a separate bowl, whisk together flour, brown sugar, cinnamon, pumpkin pie spice, and salt. Add the cooled melted butter and mix until the streusel is evenly combined and forms small clumps. If clumps aren't forming or the streusel is too wet, add more flour, 1 tablespoon at a time. Sprinkle the streusel mixture evenly over the pumpkin bread batter. Do not press the streusel into the bread. Use all of the streusel (yes, it's a lot!).
BAKE: Bake for 45-60 minutes or until a toothpick inserted in the center comes out mostly clean or with a couple of moist crumbs (not wet). My oven generally takes right about 55 minutes. Cool the bread in the pan for about 10 minutes. Working slowly and carefully, gently remove the bread by inverting onto a wire cooling rack.
GLAZE: Whisk together the glaze ingredients. Add more maple syrup (or milk), 1 teaspoon at a time, if the glaze is too thick. Drizzle just-barely-warm bread with glaze. Let set and then cut into the bread with a sharp serrated knife. Enjoy!