Bring a large pot of salted water to a boil over high heat. Add the pasta and cook until al dente, adding the asparagus to the boiling water for the last minute of cooking time. Place the peas in the bottom of your colander, and drain the pasta and asparagus over the peas. Return to the pot.

Meanwhile, melt the butter in a saucepan over medium heat. Add the garlic and cook for 30-60 seconds, until fragrant. Combine the vegetable broth and cornstarch and slowly whisk into the butter and garlic. Bring to a boil and cook, stirring constantly, until the mixture thickens. Remove from the heat and stir in the cream, lemon juice, salt, pepper and red pepper flakes.

Pour the cream mixture into the pan with the cooked pasta, asparagus and peas and toss to coat. Stir vigorously until the pasta is coated with the sauce. Taste for seasoning, and add more salt, if needed.

Serve topped with additional cracked black pepper and lemon slices, if desired.