Step 1

Bring 12 cups of water to a boil in a large pot. Add 1 tablespoon salt and 14 ounces of spaghetti. Cook according to package instructions, minus 1 minute. In the last minute, add the frozen peas to the boiling water. Scoop out 1 cup of pasta water before draining. Drain the pasta and shake off excess water.

Step 2

In a large skillet over medium heat, melt the butter. Sprinkle the flour evenly over the butter, and whisk until smooth. Whisk constantly for 1 minute. Gradually add the milk, whisking briskly and constantly until the mixture is smooth and thickened. Whisk in the garlic powder, onion powder, ground mustard powder, and a pinch of salt and pepper.

Step 3

Remove skillet from heat. Add the shredded cheese in handfuls, stirring with a wooden spoon after each addition until mostly melted. (It's okay if it’s not completely smooth.)

Step 4

Add the drained pasta and peas to the skillet. Use tongs to toss everything together until the sauce evenly coats the pasta. Gradually stir in reserved pasta water, adding just enough to achieve a creamy consistency. Taste and adjust the salt as needed—cheese loves salt to bring out its flavor!

Step 5

Serve immediately, topped with freshly grated Parmesan cheese. Enjoy!