Fill a large pot three-quarters full with water, bring it to a rolling boil over high heat, and season generously with salt.

Add the pasta to the boiling water and cook for 8 minutes, about 1 minute less than package directions, until just under al dente.

While the pasta cooks, melt the butter in a large skillet over medium heat, add the minced garlic, and cook for 1 minute, stirring constantly, until fragrant.

Pour the heavy cream into the skillet, stir to combine, and let it warm through for 2 minutes over medium heat.

Add the frozen peas to the cream mixture and cook for 3 to 4 minutes, stirring occasionally, until the peas are heated through and the sauce slightly thickens.

Drain the pasta in a colander, reserving 1 cup of the cooking water for the sauce.

Add the drained pasta to the skillet, toss to coat, and add the reserved pasta water a splash at a time until you reach your preferred sauce consistency.

Stir in the Parmesan cheese, season with salt and black pepper to taste, and sprinkle with red pepper flakes and parsley if using before serving.