Prepare for baking: Preheat the oven to 425 F. Line a muffin tin with paper liners (if using) and spray the edges of the lined muffin cavities with baking spray.
Mix the wet ingredients: Combine the wet ingredient together. Whisk until the sugar has fully dissolved and no traces of starter and eggs remain.
113 g sourdough discard, 113 g unsalted butter, 75 g buttermilk, 200 g Imperial Sugar Extra Fine Granulated Sugar, 2 large eggs, 12 g vanilla extract
Mix the batter: Add a third of the dry ingredients into the wet ingredients and stir until no dry bits of flour remain. Fold in the flour in thirds, being careful not to overwork the batter. It’s ok if a few traces of dry flour remain after the last addition.
200 g all-purpose flour, 10 g baking powder, 6 g Kosher salt
Fold in the blueberries: Toss the blueberries in a tablespoon of flour. Fold the blueberries into the batter.
216 g blueberries, 9 g all-purpose flour
Fill two muffin tins: Divide the muffin batter in 12 portions (about 86 to 90 grams in each cavity). Sprinkle tops with Imperial Sugar Extra Fine Granulated Sugar.
25 g Imperial Sugar Extra Fine Granulated Sugar
Bake: Bake the muffins for 15. Turn the temperature down to 375 F and continue baking for 5 minutes.
Enjoy and store: Allow the muffins to cool in the muffin tin for 15 minutes. These are best eaten the day they are baked but they can be stored in an airtight container at room temperature for up to 3 days.