Prepare the dough:
Place the milk, melted butter, and salt in a bowl. Stir until well combined.

Make the dough (continued):
Sift the cake flour into the butter-milk mixture. Add the instant yeast and baking soda, then mix with a spatula until combined.
Add the chopped scallions and sesame seeds, then knead by hand until a cohesive dough forms. Wrap the dough and refrigerate for 30 minutes.

Shape the dough:
After resting, place the dough on a surface lined with parchment paper. Place another sheet of parchment on top. Gently press the dough with your hands to flatten, then use a rolling pin to roll the dough out to a thickness of about 1/8–3/16 inch (3–5 mm).

Cut the crackers:
Use a rectangular or round cookie cutter to cut out shapes from the dough. Transfer each cracker to a nonstick baking sheet. Gather the dough scraps, re-roll, and cut more crackers until all the dough is used.

Bake the crackers:
Preheat the oven to 350°F (180°C) for 10 minutes. Place the baking sheet in the oven and bake for about 15 minutes, or until the crackers are golden brown.

Finished product:
The crackers are golden, crispy, perfectly salty, rich with sesame, and very fragrant with scallions. Delicious!