Season 900g of cubed skinless, boneless chicken breasts with salt and pepper. Melt 2 tablespoons of unsalted butter in a large heavy pan over medium-high heat and brown the chicken.
Add 1 medium-large diced onion and cook until translucent. Add 3 minced garlic cloves and cook until fragrant.
Stir in 425g of canned tomato sauce and 1 tablespoon of ketchup, and simmer for 2-3 minutes.
Add 1½ cups of heavy cream and simmer uncovered for about 5 minutes, until the chicken is cooked through.
