Preheat oven to 350F. Bring large pot of salted water to a boil.
Cut the cauliflower into medium-sized florets. Grate the cheese.
Add cauliflower florets to the boiling water, and cook 5-7 minutes, or until tender. Drain, reserving 1 cup of the cooking liquid, and set aside.
Melt butter in same pot over medium heat. Pour half of the melted butter in a small bowl and set aside.
Into the butter, whisk in flour, and cook 1 minute, stirring constantly. Whisk in milk, garlic, and reserved cooking liquid, and cook 7-10 minutes, or until sauce is thickened, whisking constantly.
Meanwhile, separate the eggs and set the whites aside for another use.
Once the sauce has thickened, remove it from the heat and stir in cheese, nutritional yeast, cayenne pepper, and egg yolks until cheese is melted. Fold in cauliflower.
Coat a 13 x 9 inch casserole dish with more butter or coconut oil. Spread cauliflower mixture in baking dish, and sprinkle with breadcrumbs. Drizzle reserved melted butter over the breadcrumbs. Bake 30 minutes, or until casserole is hot and bubbly and breadcrumbs are crisp and brown.