01 - Preheat oven to 425°F. Line a baking sheet with parchment paper.
02 - In a skillet over medium heat, cook diced Chinese sausage for 2–3 minutes until fragrant and lightly browned. Drain excess fat and let cool.
03 - In a large bowl, whisk together flour, baking powder, baking soda, salt, and sugar until well combined.
04 - Add cold, diced butter to flour mixture. Using a pastry cutter or fingertips, work butter into flour until mixture resembles coarse crumbs with pea-sized butter pieces remaining.
05 - Stir cooled sausage, scallions, and sesame seeds into the flour-butter mixture until evenly distributed.
06 - Pour cold milk into mixture and mix gently with a spatula or hands just until a shaggy dough comes together. Do not overmix.
07 - Turn dough onto lightly floured surface. Pat into 1-inch thick rectangle. Fold dough in half, pat out again, and repeat once more to create flaky layers.
08 - Cut rounds using 2.5-inch biscuit cutter, pressing straight down without twisting. Gather scraps and repeat, handling dough as minimally as possible.
09 - Place biscuits on prepared baking sheet. For softer sides, arrange close together; for crispier edges, space 2 inches apart.
10 - Brush tops with beaten egg if desired for golden shine.
11 - Bake for 16–18 minutes until tops are golden brown and biscuits sound hollow when tapped on bottom.
12 - Cool on baking sheet for 5 minutes before transferring to wire rack. Serve warm.