Bring a large pot of salted water to a boil, add fettuccine, and cook until al dente, about 8–10 minutes. Reserve ½ cup pasta water before draining.

In a skillet, heat olive oil over medium heat. Sauté garlic until fragrant, then add spinach and cook until wilted, about 3–4 minutes.

Blend the spinach and garlic mixture with heavy cream, Parmesan, salt, black pepper, nutmeg, and lemon juice until smooth. Return to skillet over low heat.

Blanch asparagus in boiling water for 2 minutes, then add peas and blanch for an additional minute before draining.

Combine drained fettuccine with the creamy sauce and fold in asparagus and peas. Serve immediately with garnishes.