Mound the flour and fine salt on a clean counter or in a wide bowl and make a well. Add the warm water in three additions, mixing with your fingers until a shaggy dough forms. Knead for 8 minutes until the dough is smooth and springs back slowly when pressed. If it feels stiff, add water 1 tsp at a time.

Shape the dough into a ball, cover it with an upturned bowl or plastic wrap, and rest for 30 minutes at room temperature.

Dust a 33 x 46 cm / 13 x 18 inch sheet pan with the semolina. Cut the dough into 6 pieces and keep 5 covered. Roll one piece into a rope about 1 cm thick, cut it into 2 cm lengths, then press each piece with your thumb and drag it toward you so it curls into a small open shell. Transfer to the pan and repeat with the remaining dough. When about half is shaped, set a 5-liter / 5-quart pot with 4 liters / 4 quarts of water and the coarse salt over high heat.

When the water boils, add the pìpi and stir once. Boil for 5 to 7 minutes, until a piece bitten in half is tender with a slight chew and no chalky core. Meanwhile, melt the butter in a 28 cm / 11-inch skillet over medium heat. Add the sage and garlic and cook for 3 to 4 minutes until the butter foams, smells nutty and shows amber flecks. Remove the garlic.

Scoop out 60 ml of pasta water, then lift the pìpi into the skillet with a spider strainer. Take the skillet off the heat, add the water, Casera and half the Grana Padano, and toss for about 1 minute until the cheese softens and the sauce turns glossy. Serve within 5 minutes with the remaining Grana Padano and black pepper.