Making biscuits is one of my favourite weekend activities. But making a good biscuit is tough. You need to get lots of great, fluffy layers and a crispy top. They take practice, so what better time to start than now!
2½ teaspoons baking powder
2 teaspoons kosher salt
2 teaspoons sugar
¼ teaspoon baking soda
3½ cups all-purpose flour, plus more for surface
1 cup (2 sticks) chilled unsalted butter, cut into ½-inch pieces, plus more, melted, for brushing
1 cup chilled buttermilk
Preheat oven to 425°. Pulse baking powder, salt, sugar, baking soda, and 3½ cups flour in a food processor to combine. Add chilled butter and pulse until largest pieces of butter are the size of a pea. Transfer to a large bowl and gradually drizzle buttermilk over top, tossing with a fork as you go to incorporate. Knead mixture a few times in bowl until a shaggy dough forms (mixture will look a little dry), then turn out onto a clean surface and pat into a 1″-thick square.
Using a knife or bench scraper, cut dough into 4 pieces. Stack pieces on top of one another, sandwiching any loose dry bits of dough between layers, and press down to flatten. Lift up dough with bench scraper and dust surface with flour. Roll dough into a 1″-thick rectangle and trim a thin border around sides of dough to create clean edges. Cut into a 4×3 grid to make 12 biscuits (don’t reroll scraps). Transfer to a parchment-lined baking sheet, spacing 2″ apart; freeze 10 minutes.
Bring a large pot of salted water to a boil. Cook spaghetti until al dente, 6 to 7 minutes. Meanwhile, fill a large serving bowl with hot water or warm it in a low oven. Lightly beat the eggs in a small dish. Just before pasta is done, return pan with sausage to low heat. When pasta is done, slowly beat about a tablespoon of pasta water into eggs. Then drain the pasta.
Brush tops of biscuits with melted butter and place in oven. Reduce oven temperature to 400° and bake biscuits until deep golden brown on bottom and golden on top, 20–25 minutes.