Step 1

Heat oven to 375°F. Cook the pasta according to package directions. Reserve 1/4 cup of the cooking liquid, drain the pasta and return it to the pot.

Step 2

Meanwhile, spread the walnuts on a rimmed baking sheet and toast until fragrant, 6 to 8 minutes.

Step 3

While the walnuts are toasting, heat the oil in a large skillet over medium-low heat. Add the onion and 1/4 tsp each salt and pepper and cook, covered, stirring occasionally, until very tender, 6 to 8 minutes. Stir in the garlic and cook for 1 minute.

Step 4

Whisk in the milk and bring to a simmer. Whisk in the cream cheese, Parmesan and nutmeg and simmer, stirring occasionally, until slightly thickened, 2 to 3 minutes.

Step 5

Toss the pasta with the cream sauce, blue cheese and walnuts, adding some of the reserved cooking liquid if the pasta seems dry. Top with the chives.