In a large pot, simmer the chicken breasts until tender.

Once cooked, remove from the pot and set aside.

Cook the frozen broccoli in salted water according to package instructions.

Drain the broccoli and set aside.

Preheat the oven to 350°F (175°C).

Grease a casserole dish with cooking spray.

Arrange the cooked broccoli in the greased casserole dish.

Slice the cooked chicken breasts in half horizontally to create thinner pieces.

Place the halved chicken breasts on top of the broccoli in the casserole dish.

In a mixing bowl, combine the cream of chicken soup, mayonnaise, and lemon juice.

Mix until well combined.

Pour the mixture evenly over the chicken in the casserole dish.

Sprinkle the shredded cheddar cheese over the top of the chicken and sauce mixture.

In a small bowl, mix the soft bread crumbs with melted butter.

Sprinkle the buttered bread crumbs over the cheese layer.

Bake the casserole in the preheated oven for 25 minutes, or until the cheese is melted and bubbly, and the casserole is heated through.

Serve hot with rice or potatoes for a complete meal.