Season chicken, if desired, with salt and pepper. Melt 1 Tbsp (15 mL) margarine in large nonstick skillet over medium-high heat and cook chicken, in batches if necessary, until golden brown, about 4 minutes. Remove chicken and set aside.
Add onion to same skillet and cook, stirring frequently, until tender, about 8 minutes. Stir in garam masala, ginger and garlic and cook, stirring, until fragrant, about 30 seconds. Add tomato sauce, Knorr® Homestyle Stock Chicken and 1/2 cup (125 mL) water and bring to a boil over medium-high heat. Reduce heat and cook, stirring occasionally, until slightly thickened, about 5 minutes. Stir in half and half cream and cook until slightly reduced, about 3 minutes.
Add chicken and cook until thoroughly cooked, about 2 minutes. Serve, if desired, sprinkled with chopped cilantro.