Start boiling a pot of salted water. Add pasta when ready, and cook until al dente (slightly firm). Reserve 1 cup of pasta water before draining (to be used later).
In a large saute pan, heat up a drizzle of olive oil on medium-high heat until hot. Add sliced cabbage and minced garlic. Season with salt and pepper to taste. Cook, stirring occasionally, 3-4 minutes, or until slightly softened.
To the cabbage, add the sage and as much of the red pepper flakes as you wish, depending on how spicy you'd like it. Add more salt and black pepper to taste. Cook, stirring frequently, 1 to 2 minutes, or until fragrant.
Add 1/4 cup of the pasta water to the cabbage and cook another 1 to 2 minutes while stirring frequently.
Add the cooked pasta, butter, and half the shredded cheese, and 1/2 the remaining pasta water to the cabbage pan. Add more salt and pepper to taste, cook on medium-high, stirring vigorously, 1 to 2 minutes, or until thoroughly coated. If pasta seems dry, keep adding more pasta water to achieve desired consistency. Remove from heat when done.
Optional: add browned and drained ground turkey to the cabbage pasta, and mix well.
Serve immediately, topping with more sage and red pepper flakes if desired, and generous amount of shredded cheese. Buon Appetito!