Cook the cauliflower in boiling water for about 10 minutes, then drain.
In a hot skillet, melt the garlic butter and sauté the mushrooms for a few minutes over medium heat.
Spread the cooked cauliflower in a 9 x 13-inch oven dish.
Add ham and sautéed mushrooms.
In a mixing bowl, whisk together the cream of celery soup, vegetable broth, and dry mustard.
Scatter the brie cheese cubes evenly over the vegetables and ham in the dish.
Pour the creamy mixture into the dish.
Add the English muffin cubes on top.
Sprinkle the shredded mozzarella cheese over the casserole.
Bake in the preheated oven for about 30 minutes.
Finally, you can put the dish under the broiler until golden brown.
Serve hot.
Notes / Tips / Wine Advice:
Wine Advice:
Given the richness of this dish, opt for a medium-bodied white wine such as Chardonnay or a light-bodied red wine like Pinot Noir. For a non-alcoholic option, a sparkling apple cider would complement the flavors well.