Beat the softened cream cheese. Add the cream of chicken soup, milk, chicken broth, minced onion, minced garlic, coarse ground black pepper, and kosher salt.
Stir in the diced chicken and 1 cup of shredded cheddar cheese. Spread the mixture in a greased casserole dish (2.4-quart or larger). Top with the remaining 1/2 cup of shredded cheddar cheese.
Mix the crushed Ritz crackers and melted butter together and sprinkle over the casserole.
Bake at 350˚F for 25-30 minutes, until the filling is bubbly and the casserole is golden brown on top.