1. Preheat your oven to 400 F (200 C). Lightly grease a 12-cup muffin tin or line it with paper liners. In a large mixing bowl, whisk together the all-purpose flour, 1/4 cup granulated sugar, baking powder, baking soda, and salt. Make sure these dry ingredients are thoroughly combined to ensure even leavening.

2. Add the cold, diced butter to the dry ingredients. Using a pastry blender, your fingertips, or two knives, cut the butter into the flour mixture until it resembles coarse crumbs with some pea-sized pieces remaining. This step is key for creating flaky biscuits.

3. In a separate medium bowl, whisk together the sourdough starter discard, buttermilk (or homemade substitute), and vanilla extract until well combined. The mixture should be smooth.

4. Pour the wet ingredients into the dry ingredients. Stir gently with a spoon or spatula until just combined. Be careful not to overmix; the dough will be shaggy and a bit sticky, but that’s perfectly normal for a tender biscuit muffin. Overmixing develops gluten, leading to tough muffins.

5. Divide the dough evenly among the 12 muffin cups. In a small bowl, combine the 1/4 cup granulated sugar and ground cinnamon for the topping. Sprinkle this cinnamon sugar mixture over the tops of each muffin. Then, evenly distribute the sliced almonds over the cinnamon sugar.

6. Place the muffin tin into the preheated oven and bake for 18-20 minutes, or until the tops are golden brown and a wooden skewer inserted into the center of a muffin comes out clean. The muffins should also feel firm to the touch.

7. While the muffins are still warm, melt the 2 tablespoons of butter. Brush the tops of the baked muffins with the melted butter. This adds a lovely sheen and extra richness. Let them cool in the muffin tin for a few minutes before transferring them to a wire rack to cool completely, or serve them warm for the best experience.