Preheat the oven to 350 degrees F (175 degrees C).
Bring about 2 inches of water to a boil in a large pot. Add cauliflower and carrots, and boil for about 7 minutes, until fork tender. Drain well, and transfer to a 9x13 inch baking dish.
While the vegetables are cooking, combine the egg yolks, salt, lemon juice and hot pepper sauce in a blender or food processor. Blend for a few seconds to mix, then continue to blend while slowly pouring in 1/2 cup of hot melted butter. Continue blending until thickened. Pour this sauce over the vegetables in the baking dish. Stir together the cracker crumbs and remaining butter; sprinkle over the top of the casserole.
Bake for 20 minutes in the preheated oven, or until the casserole is bubbling, and the top is toasted. Let cool slightly before serving.