Preheat your oven to 325°F (160°C).

In a mixing bowl, prepare the stuffing by combining breadcrumbs, chopped onion, salt, thyme, pepper, melted butter, and water.

Mix well.

Pound the chicken breasts to flatten them slightly for easier stuffing.

Divide the stuffing mixture evenly among the chicken breasts, placing it in the center of each.

Securely seal each stuffed chicken breast with toothpicks or skewers to prevent the stuffing from falling out during baking.

In a paper or plastic bag, combine flour, salt, paprika, and pepper.

Shake each stuffed chicken breast in the bag to coat evenly with the flour mixture.

Place the coated chicken breasts in a greased baking dish.

Brush the tops of the chicken breasts with any remaining melted butter.

Bake in the preheated oven for 1 to 1 1/2 hours, turning once halfway through cooking, until the chicken is cooked through and golden brown.

Once cooked, remove the toothpicks or skewers from the chicken breasts.

Sprinkle chopped parsley over the chicken breasts before serving.

Serve with mushroom sauce on the side.