Cheesy Broccoli Stuffed Chicken Breasts

For the Broccoli Filling:

• 2 cups broccoli florets, finely chopped
• 1 cup shredded cheddar cheese
• 1/2 cup cream cheese, softened
• 1/4 cup grated Parmesan cheese
• 2 cloves garlic, minced
• 1 teaspoon dried oregano
• Salt and black pepper, to taste

For the Sauce:

• 1 cup chicken broth
• 1/2 cup heavy cream
• 1 tablespoon Dijon mustard
• 1 tablespoon cornstarch (optional, for thickening)
• Salt and black pepper, to taste