Cook the pasta per package instructions. Liberally salt the water. Reserve a cup of pasta water before draining. I hate it when I forget to do that!
Prepare the protein. You'll vary the process depending on the protein. For boneless, skinless chicken thighs, cut them in 1" pieces and sprinkle salt and pepper and a seasoning, such as paprika, or onion powder, on both sides. Let these chunks dry-marinate in a bowl while you attend to other prep. For other protein sources, such as shrimp, the prep involve different seasoning, but is basically the same.
Peel and dice the onion.
Mince the sun-dried tomatoes and set aside.
In the skillet over medium-high heat, melt the butter and add the oil if using. Cook until the impurities are bubbled out of the butter. Less than a minute.
Stir in the minced garlic and cook until fragrant. Less than a minute.
Add the protein to the skillet and cook until it's just barely done. This will be 8-10 minutes for chicken or ground meat, only 3-4 minutes for shrimp. Don't overcook either one or you'll robbing yourself of juiciness.
Remove the chicken and/or shrimp to a bowl to avoid over-cooking. You'll add it back later.
Add seasonings, sundried tomatoes. Combine thoroughly and let simmer for 2-3 minutes. Turn down the heat a bit if things are too energetic.
Add the spinach or other vegetable. Let fresh spinach thoroughly wilt. Let cooked vegs get warmed through and integrated with the sauce.
Add back the chicken and/or shrimp. Mix all together and heat through evenly.
Add finely grated Parmesan cheese and mix well.
Add cooked pasta and combine well. Let your concoction sit for a bit on very low heat. Give your pasta a few minutes to take in its new surroundings. If things get too thick, use some leftover pasta water to get the sauciness you like.
Add salt and pepper to taste, fresh or dried parsley, and more Parmesan to finish just before serving. You have created a dish that is comforting, sophisticated, and scrumptious for just about anyone. There are so many ways to vary this that you can make new and favorite versions over and over and no one will know how easy it's become to make something really special and pretty fast on a week night. See Notes below for more ideas.