Heat the oven to 425°F (220°C). Line a baking sheet with parchment paper.

In a large bowl, whisk together the flour, baking powder, baking soda, and salt.

Add the cold butter and work it into the flour using a pastry cutter or your fingertips until the mixture resembles coarse crumbs with several pea-sized pieces of butter remaining. Those larger pieces help create flaky layers.

Pour in the cold buttermilk and gently stir with a rubber spatula until a shaggy dough forms. Do not knead or mix until perfectly smooth.

Turn the dough onto a lightly floured surface and gently pat it into a rectangle about 3/4 inch (2 cm) thick. Fold the dough in half, rotate it, and gently pat it back to the same thickness. Repeat this fold once more.

Pat the dough to about 3/4 inch (2 cm) thick. Cut 8 biscuits with a 2 1/2-inch (6 cm) round cutter, pressing straight down without twisting. Arrange them on the prepared baking sheet with the sides just touching for softer edges.

Bake for 12 to 15 minutes, until the tops are golden brown and the sides look fully set. Transfer to a rack and let them rest for 5 minutes.

While the biscuits bake, heat a 10-inch skillet over medium heat. Add the chorizo and cook for 5 to 7 minutes, breaking it into small crumbles. Continue until it is browned and fully cooked, with no raw meat remaining. Ground sausage should reach 160°F (71°C) internally.

Sprinkle the flour evenly over the cooked chorizo: Stir continuously for about 1 minute. The flour should coat the sausage and absorb most of the rendered fat, forming a thick paste.

Slowly pour in the milk while whisking continuously, scraping the bottom and sides of the skillet. Add it in several additions rather than all at once. The mixture will initially look thin and then begin to thicken.

Bring the gravy to a gentle simmer over medium-low heat. Cook for 4 to 6 minutes, stirring frequently, until it is thick enough to coat the back of a spoon. Stir in the garlic powder, black pepper, and salt.

If the gravy becomes too thick, whisk in a small splash of milk. If it remains too thin after simmering, continue cooking for another 1 to 2 minutes. Taste before adding additional salt because chorizo can vary considerably in saltiness.

Split the warm biscuits and spoon the chorizo gravy generously over the cut sides. Finish with optional cilantro, green onions, or red pepper flakes and serve immediately.