If using Italian sausage, remove from casing. Before cooking shrimp, heat a large non-stick pan over medium-high heat. Add 1 tsp. olive oil and Italian sausage to hot pan. Break into smaller pieces with a spoon until no pink remains, 4-6 minutes. Transfer sausage to a plate and tent with foil. Wipe pan clean and reserve for shrimp.
If using 16 oz. shrimp or scallops, pat dry and season with 1/4 tsp. salt. Follow same instructions as 8 oz. shrimp, cooking in batches if necessary.
If using diced chicken, pat dry and season with 1/4 tsp. salt. Follow same instructions as shrimp Step 3, cooking over medium-high heat and stirring occasionally until chicken reaches minimum internal temperature, 5-7 minutes.