Cook the cauliflower in boiling water for about 10 minutes and drain.

In a hot skillet, melt butter with garlic and sauté the mushrooms a few minutes over medium heat.

Spread the cooked cauliflower in a 9 x 13 oven dish.

Add ham and mushrooms.

In a bowl, whisk together the cream of celery, vegetable broth and dry mustard.

Scatter the brie cheese cubes evenly over the vegetables and ham.

Pour the creamy mixture into the dish.

Add the bread cubes on top.

Top with grated cheese.

Bake at 350 F for about 30 minutes.

Finally, you can put the dish under the broiler until golden brown.