In a large pot, bring salted water to a boil. Add rotini pasta and cook until al dente, about 8-10 minutes. Reserve ¾ cup of pasta water before draining.

In a large skillet, heat olive oil over medium-high heat. Add ground beef and Italian sausage; cook until browned, about 6-8 minutes. Drain excess grease.

Push meat to the side and melt unsalted butter in the skillet. Add minced garlic and sauté for 1 minute until fragrant.

Stir garlic into the meat mixture. Cook together for 1 minute, then add fresh spinach.

Cook spinach for 1-2 minutes until wilted, adding brightness and freshness to the dish.

Pour in heavy cream and grated Parmesan cheese, mixing until cheese melts. Keep the heat low.

Gradually add reserved pasta water until desired sauce consistency is achieved. Taste and adjust seasoning.

Add drained rotini pasta to the skillet. Toss to coat pasta evenly with the sauce and meat.

Season with salt, black pepper, and crushed red pepper flakes to taste. Mix well.

Transfer to serving plates and garnish with extra grated Parmesan if desired. Serve hot.