Melt butter in a sauce pan, add flour 1/3 at a time and stir with a wire whisk to form a roux. Add half & half one cup at a time and stir with each addition. Stir vigorously to avoid lumps. Allow to simmer at low heat until the sauce thickens. Turn off the heat and add parmesan cheese, salt, pepper, hot sauce and one cup of shredded colby cheese, stir to combine. The sauce should be thick, because the vegetables will weep a little water as they cook and thin the sauce down. Set aside.
* see bechamel recipe in sauce chapter for more detail on this white bechamel sauce
Bread Crumb Mixture:
Place bread, butter and spices in a food processor and process until crumb like. Mix in 1 cup shredded cheddar or colby cheese. Set aside.
Cut broccoli and cauliflower into florets and cook in boiling water for two minutes. Do not overcook the vegetables or the finished product will be mushy. Remove vegetables from water, drain well and place in casserole dish.
Pour sauce over vegetables and top with bread crumb mixture.
Bake the casserole in a 400-degree oven until golden brown and gorgeously bubbly.