1. Cook pasta according to package directions. Drain pasta and cut into small pieces, about 1/2 cm.
2. Heat butter in a small saucepan over medium heat. Add mushrooms and cook for 6 to 8 minutes, or until soft. Place mushrooms on paper towel to absorb excess moisture.
3. Add Heinz Chicken Casserole with Vegetables and Rice Jar, chopped mushrooms and pesto to a small saucepan over medium heat. Stir until combined and heated through, about 2 to 3 minutes.
4. Check temperature before serving.
5. Serve portion in a bowl and refrigerate remainder for another meal.