Preheat the oven. Set the oven to 350°F and prepare an 8×8-inch baking dish.
Prepare the broccoli. Bring a pot of water to a boil, then turn off the heat. Add the frozen broccoli and allow it to soften in the hot water for approximately 7 minutes, checking that it remains firm enough to hold its shape. Drain thoroughly and gently press out excess moisture.
Make the cheese sauce. Add the cubed Velveeta and evaporated milk to a small saucepan over low to medium-low heat. Stir until the cheese has completely melted into a smooth sauce. Do not allow it to boil. Mix in the salt and black pepper.
Combine the broccoli and cheese. Transfer the drained broccoli to the baking dish. Pour the melted cheese sauce over the broccoli and gently stir until evenly coated.
Prepare the Ritz topping. Crush the Ritz crackers in a zip-top bag, leaving some larger crumbs for texture. Add the melted butter and mix until the crackers are coated.
Add the topping and bake. Spread the buttery Ritz crumbs evenly over the broccoli and cheese mixture. Bake for approximately 20 minutes, until the casserole is heated through and the topping is golden.
Rest and serve. Remove the casserole from the oven and let it cool slightly before serving.