Set the cottage cheese in a fine-mesh sieve over a bowl to drain for 5 minutes. While it drains, dice the onion, mince the garlic, and bring 3 L of water with 1 tbsp kosher salt to a boil in a 5-quart / 4.7 L pot.

Blend the drained cottage cheese, eggs, Parmesan and 1/4 tsp fine salt in a food processor for about 30 seconds until smooth. Scrape into a bowl, add 200 g flour, and stir with a spatula until no dry patches remain. The dough will be soft and tacky, like thick biscuit dough.

Flour the counter and your hands generously. Divide the dough into 4 pieces, roll each into a rope about 2 cm / 3/4 inch thick, and cut into 2.5 cm / 1-inch pieces. You'll get about 80 to 100 gnocchi. Move them to a floured sheet pan, 33 x 46 cm / 13 x 18 inch.

Let the gnocchi rest for 10 minutes so the surface dries a little. During the rest, drop one into the boiling water as a test. If it holds its shape after 3 minutes, carry on. If it falls apart, knead 2 tbsp flour into the remaining dough, then re-roll and re-cut.

Heat the olive oil in a 30 cm / 12-inch deep skillet over medium-high heat. Add the sausage and break it up with a spoon. Cook for 5 to 6 minutes until browned with no pink left, 165 F / 74 C. Add the onion and cook 3 minutes until soft, then stir in the garlic for 30 seconds.

Pour in the crushed tomatoes and add the black pepper. Simmer over medium-low heat for 8 minutes, stirring now and then, until the sauce is thick enough to leave a trail when you drag a spoon through it.

While the sauce simmers, cook the gnocchi in two batches in gently boiling water. Each batch floats in about 2 minutes, then give it 1 more minute, 3 minutes total. Lift with a slotted spoon straight into the sauce, and keep the pot water for later.

Add the spinach and up to 120 ml of the gnocchi cooking water to the skillet. Fold gently for about 2 minutes until the spinach wilts and the sauce clings to the gnocchi. Tear the basil over the top and serve right away.