Season chicken with 1 teaspoon salt and 1/4 teaspoon black pepper. Cook in a skillet until golden, then transfer to a plate.
Cook garlic, tomato paste, and red pepper flakes until fragrant. Add broth, pumpkin, Parmesan, cream, lemon juice, and salt; simmer. Return chicken and cook until sauce thickens.
Stir in half of basil; season. Garnish with remaining basil, shaved Parmesan, and red pepper flakes before serving.
Notes
Use fresh basil for the best flavor and adjust red pepper flakes to taste.