Grate 8 tablespoons unsalted butter directly into a large mixing bowl using a cheese grater. Add 2 ½ cups all-purpose flour to the bowl and use a bench scraper to cut it into the butter with a chopping motion. Add 1 cup buttermilk, ½ cup sourdough starter discard, 1 ½ teaspoon baking powder,½ teaspoon baking soda, 1 tablespoon sugar, and 1 teaspoon fine sea salt. Mix with a sturdy spatula until well combined. Finally, add 1 ½ cups sharp cheddar cheese and ½ cup green onions and mix with the spatula until it is just well combined. Don't overmix.

Grate the butter into a large mixing bowl. Add the flour and use a bench scraper or fork to mix the butter into the flour until it looks like small pea-sized crumbs. Add the sourdough starter discard, buttermilk, cheese, green onions, and sugar. Stir with a stiff spatula until everything is well combined. Cover the bowl and let it rise on the counter for 10-12 hours.Before scooping out the biscuits, mix the salt, baking soda, and baking powder in a small bowl with a fork, breaking up any lumps. Sprinkle half of this mixture over the dough and work it in with your hands. Then sprinkle the remaining half and keep mixing until everything is fully combined.

Preheat your oven to 400°F (204°C). Line a large baking pan with parchment paper.

Use a large ice cream scooper to scoop 12 biscuits onto the parchment paper-lined baking sheet. Each biscuit weighs about 73-75 grams. The dough will be sticky, so you will need to use your fingers or a spoon to assist in dropping them onto the baking sheet.

Bake for 20-25 minutes, or until the tops are golden brown. Remove and serve warm.