Break cauliflower up into florets and cut sausage into rounds, then half those. Toss the cauliflower and sausage together in a large mixing bowl with the onion powder, garlic powder, salt, and pepper. Pour the mixture into a large baking dish, adding the peas if you'r using them, and set aside.
In a saucepan, melt the butter and add the flour, mixing to make a roux. Add the chicken stock and stir over medium-high heat until the sauce starts to thicken. Add 1 cup of the grated cheese and stir until smooth. Pour the sauce over the cauliflower and kielbasa mixture and place the baking dish in the oven for 40 minutes.
At the 40-minute mark, sprinkle the remaining half cup of cheese over the top of the dish and put it back in the oven for 10 minutes or so until it gets brown and bubbly.