Make the streusel: Cut butter into all-purpose flour and cinnamon using a fork or your fingertips. Stir brown sugar into the mixture using a spatula until walnut or pea-sized pieces form. Refrigerate while you prepare the batter.
4 grams ground cinnamon, 42 grams unsalted butter, 40 grams all-purpose flour, 50 grams brown sugar
Melt butter: Melt the butter in a small saucepan over medium heat. Transfer the melted butter to a large mixing bowl, add spices to bloom. Let the butter cool completely before continuing.
113 grams unsalted butter, ½ teaspoon ground cinnamon, ½ teaspoon ground ginger, ¼ teaspoon ground nutmeg, ⅛ teaspoon ground cloves, ⅛ teaspoon ground all-spice
Mix the wet ingredients: Whisk the brown sugar into the butter until fully dissolved. Stir the egg and vegetable oil into the mixture. Add in the pumpkin puree, sourdough discard and milk until fully incorporated and no traces of discard remain.
200 grams brown sugar, 28 grams vegetable oil, 1 large egg, 226 grams pumpkin puree, 56 grams sourdough discard, 28 grams whole milk
Make the batter: Fold the baking soda, baking powder, salt and a third of the flour mixture into the wet ingredients. Gently stir the flour in until no traces remain.
210 grams all-purpose flour, 4 grams baking powder, ¼ teaspoon baking soda, 6 grams salt
Fold the flour in a third at a time to prevent lumps. Cover the bowl with plastic wrap and let the batter rest while the oven preheats.
Prep: Preheat the oven to 450 F with the rack in the middle. Line a muffin tin with paper liners. Set aside.
Portion out batter: Divide the batter evenly among the crevices of the prepared muffin tin (about 80 to 90 grams or 6 tablespoons of batter in each). Top the batter with streusel.
Bake: Place the muffin tin on the middle rack of the oven, close the door and immediately turn down the temperature to 375 F.
Bake the muffins for 20 to 25 minutes, or until a toothpick inserted in the center comes out clean. Do not open the door too soon or your muffins will sink!
Let the muffins cool in the tin for 15 minutes before turning them out on a wire rack.
Enjoy and store: Serve the muffins fresh from the oven and enjoy! Store any leftovers in an airtight container for up to 5 days.