Turn on the broiler and line a baking sheet with parchment paper. Slice the baguette into 3/4" slices. I slice them slightly on a diagonal to make them slightly larger and more attractive. Light brush the tops with olive oil, and broil until toasted. They should be well-toasted since you're only toasting one side. Set aside.
Heat the oven to 350˚F and line a second baking sheet with parchment paper. Remove each large floret from the stalk, and carefully slice into 3 small slabs through the stalk of the floret. Two of the slabs, when laid flat on a table, have the rounded tops of the floret. Shave it off to flatten, making the cauliflower pieces equal thicknesses of roughly 1/2 inch. Gently rub them all over with olive oil, and lay them on the second baking sheet. Lightly dust them with salt and pepper, and roast for 15 minutes. Flip them over and roast until tender, about another 10 minutes.
Melt the butter in a medium saute pan over medium heat. Core the apples and thinly slice, leaving on the skin. Salute the apple slices until tender, about three minutes. Remove from the pan and saute the garlic, raisins and pepitas until warm and fragrant, about two minutes.
Smear at least 1/4 tsp Prepared Horseradish on the untoasted side of each of the bread slices. Lay 2 apple slices on top, arrange 1 tsp of the raisin mixture on top of the apples, and anchor with a floret piece of cauliflower. Drape a piece of cheese over the top of each floret. Slide into the oven (still at 350˚F) and bake until the cheese has melted, about 3 - 4 minutes.