Preheat oven to 375.
Chop one head of broccoli into bite size pieces.
Bring 3 cups of low sodium chicken broth to a boil. Add 1 1/2 cup long grain rice and the broccoli. Cover and lower heat to low. Cook for about 15 minutes until fluid is absorbed.
While rice is cooking, chop one small onion and cube two skinless boneless chicken breasts into 1/2 inch pieces.
Over medium-high heat, melt 1 tablespoon butter in a large skillet then add the chicken and onions. Cook until onion is translucent and chicken is 165 degrees internally. About 1 minute before the end point add 3-4 cloves crushed garlic. About 9-10 minutes total for me.
Remove the chicken from heat and wait for rice to finish. Then combine rice with the chicken, add 1/2 cup milk, 3 tablespoons mayonnaise, 1/2 teaspoon salt, 1/4 teaspoon pepper, 1 1/2 cups of shredded cheese of choice. Mix well.
Spray a 9 X 13 casserole dish with PAM and add mixture. Top with 1/2 cup of shredded cheese of choice.
Mix crumble top. 1 cup Panko bread crumbs, 3 tablespoons melted butter, and 1/4 cup grated Parmesan cheese. Spread over the casserole.
Bake for 30 minutes until golden brown and bubbling. Allow to rest for 10 minutes before serving to absorb fluid.