Cook the pasta:
Bring a large pot of salted water to a boil. Cook the spaghetti until al dente. Reserve 1 cup of pasta water, then drain.

Cook the sausage:
While the pasta cooks, heat olive oil in a pan over medium heat. Add sausage (crumbled) and cook for 6–8 minutes until browned. Add garlic and sauté for 1 minute. Remove from heat.

Make the carbonara sauce:
In a bowl, whisk together eggs, yolk, cheese, a good pinch of black pepper, and a splash of pasta water to temper.

Combine everything:
Add the drained pasta to the pan with sausage (off the heat). Quickly pour in the egg mixture, stirring vigorously to coat the pasta and create a silky sauce. Add more reserved pasta water as needed to loosen the sauce.

Garnish and serve:
Serve immediately, topped with extra cheese, a crack of black pepper, and parsley if desired.

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