Creamy Chicken Florentine

Name: Creamy Chicken Florentine
Ingredients: 2 tablespoons all-purpose flour; 1/2 teaspoon kosher salt , divided, plus more to taste; 1/4 teaspoon freshly ground pepper , divided, plus more to taste; 4 chicken cutlets (1 to 1 1/2 pounds total); 3 tablespoons olive oil , divided; 2 medium shallots , chopped; 8 ounces cremini mushrooms , trimmed and sliced (about 3 cups); 3 cloves garlic , minced; 1/4 cup dry white wine; 1/2 cup heavy cream; 1 ounce finely grated Parmesan cheese (about 1/2 cup); 12 ounces fresh baby spinach