Yields 6 - 8 servings.

10 ounces dry pasta (I used a combination of rotini, farfalle and penne. Any similar size would work.)
2 tablespoons butter
1/2 onion, chopped
2 cloves garlic, minced
4 ounces chive and onion cream cheese
1 cup sour cream (or plain Greek yogurt)
1 cup whole milk, heavy cream or half-and-half (I used half-and-half)
1/2 cup shredded or grated Parmesan cheese
2 cups shredded mozzarella cheese
1/2 teaspoon salt
1/2 teaspoon black pepper
Pinch crushed red pepper flakes (optional)
1 - 1 1/2 cups chopped fresh spinach
2 cups cooked chicken (cubed or shredded)
1/2 cup fresh tomatoes, cut into large chunks (I used grape tomatoes sliced in half)
Fresh basil or parsley, for garnish