Chop chicken sausage into bite-sized rounds. Chop bell peppers and onions into bite-sized chunks.
Heat large non-stick skillet to medium high heat. Drizzle with 1 tbsp olive oil.
Once the pan is heated, add chicken sausage. Cook until slightly browned (about 5 minutes), stirring frequently using a non-metal utensil.
Remove chicken sausage from pan to a large plate or bowl. Leave the pan on medium high heat for next step.
Quickly add 1 tbsp butter and 1 tbsp olive oil back to the skillet. Allow to melt; then add peppers and onions to the skillet. Cook until crisp tender (about 5 minutes).
Reduce heat to medium. Add spinach to the cooked vegetables and stire, allowing to wilt. Putting on a lid can speed up the process.
Add chicken sausage back into the pan, using a rubber scraper to make sure all those yummy juices get added back into the dish.
Turn off heat. Salt and pepper to taste, and serve! Top with freshly grated parmesan if desired.