For a richer sauce, substitute heavy cream or add a quarter cup of cream cheese during cooking. Unsweetened almond milk is suitable if a lighter version is preferred, but avoid sweetened varieties. Cornstarch can be used instead of flour for additional thickness. Boneless thighs or shrimp make fine alternatives to chicken breast. Opt for fresh spinach when possible, or thaw and drain frozen spinach thoroughly. Cook pasta al dente to prevent it from becoming mushy. Leftovers should be kept in an airtight container in the refrigerator for up to three days.