Gnoochi
Spoon the ricotta into a large, fine-meshed sieve. Set the sieve over a bowl and cover the ricotta with plastic wrap. Leave the ricotta in the refrigerator to drain overnight.

The next day, transfer the ricotta to a mixing bowl. In a separate bowl, combine the eggs and 1 teaspoon and beat  until foamy. Stir the eggs, ½ cup of the grated cheese, pepper, and nutmeg into the ricotta until thoroughly blended. Gradually stir in as much flour as necessary to form a soft and sticky dough. (Ricotta gnocchi dough is always soft and sticky, so don’t work in so much flour that you have a firm, smooth dough, or the cooked gnocchi will be tough and heavy.)

Divide the dough into 6 approximately equal pieces. On a clean, work surface lightly floured to prevent sticking, lightly dust one of the dough pieces and, with clean lightly floured hand, roll it back and forth to form a rope about ½ inch in diameter. Cut the rope of dough crosswise into ¾-inch pieces. Dust the cut gnocchi lightly with flour and toss them to separate. Repeat the process with the remaining dough.

Sauce and Assembly
In a saucepan over medium heat, melt the butter and whisk in the flour. Continue whisking for 2 to 3 minutes. Then, still whisking, gradually pour in the warm milk and increase the temperature to medium-high. Continue whisking for a few minutes until the sauce begins to thicken. Then sprinkle the cheese into the hot sauce and whisk until it is fully melted and incorporated. Season to taste with salt and pepper and turn off the heat.

Preheat the oven to 375°F. Bring 6 quarts of salted water to a boil in a large stockpot.

A few at a time, stir the gnocchi  into the boiling water. Bring the water back to a boil, stirring frequently. Cook, partially covered, stirring occasionally, until the gnocchi float to the top and are tender, about 5 minutes.

Drain the gnocchi gently and fold them gently into the sauce. Pour the sauce and gnocchi into a 2-quart baking dish or pan. Bake in the preheated oven until lightly browned, 15 to 20 minutes. at 375 degrees or until lightly browned. If needed, brown briefly under a hot broiler.. Garnish with basil and chopped chives and serve immediately.