Penne with Creamy Pesto Sauce

1 (16 ounce) package uncooked penne pasta

1 tablespoon olive oil

1 pound fresh broccoli florets

1 pound fresh asparagus, trimmed and cut into 1 1/2-inch pieces

1 (8 ounce) package sliced fresh mushrooms

¼ cup thinly sliced onion

1 clove garlic, minced

½ cup pine nuts

salt to taste

2 tablespoons butter

3 tablespoons all-purpose flour

1 teaspoon salt

2 cups milk

1 cup prepared pesto

salt and ground black pepper to taste

1 tablespoon pine nuts

Fill a large pot with lightly salted water and bring to a boil. Stir in penne and return to a boil. Cook pasta uncovered, stirring occasionally, until cooked through but still slightly firm, about 11 minutes; drain.

Heat olive oil in a large skillet over medium heat and cook and stir broccoli, asparagus, mushrooms, onion, garlic, and 1/2 cup pine nuts until the broccoli and asparagus are tender, about 8 minutes. Season with salt to taste.

Melt butter in a large saucepan over medium heat and stir in flour and 1 teaspoon salt until smooth. Slowly whisk in milk until thoroughly combined, bring to a simmer, and reduce heat to medium-low. Simmer sauce, whisking constantly, until thickened, about 3 minutes.

Remove sauce from heat and whisk in prepared pesto. Season to taste with salt and black pepper.

Pour pesto sauce into skillet with broccoli mixture; gently stir in penne pasta until thoroughly combined. Sprinkle with 1 tablespoon pine nuts to serve.