Cauliflower "mac" and cheese

Adapted from Vegetarian Times.

1 large head cauliflower, cut into florets (about 8 c.)

3 Hatch chilies, diced, or about 4 oz. canned green chilies

1 15.5-oz can fire-roasted tomatoes, drained

2 Tbsp. butter
3 Tbsp. all-purpose flour
2 c. whole milk
1 c. half and half
2 c. grated extra-sharp cheddar (I used 1 c. aged white cheddar and 1 c. sharp cheddar, packed)
1 Tbsp. dijon mustard
2 egg yolks
salt and pepper, to taste

1.5 c. fresh breadcrumbs + 2 Tbsp. butter

Preheat oven to 350 degrees F. Bring a large pot of salted water to boil, and cook the cauliflower florets for 5-7 minutes, or until just tender. Drain and add to a large bowl with the diced chilies and fire-roasted tomatoes.

Melt butter in a sauce pan over medium heat. Add the flour, and cook for 1-2 minutes, whisking constantly. Whisk in milk and cream. Cook over medium heat for 7-10 minutes until the sauce is thickened. Incorporate the cheese one handful at a time. Let the first handful melt before adding another. Once the cheese is fully incorporated, remove the pan from the heat. Allow to cool slightly. Whisk in the mustard. Add the egg yolks one at a time, whisking constantly to prevent curdling. (Or temper the yolks using a separate bowl.) Season cheese sauce liberally with salt and pepper. Pour over cauliflower and mix thoroughly. Transfer to a 9x13 pan.

In a saute pan, melt the remaining 2 Tbsp butter and toast the breadcrumbs slightly. Sprinkle bread crumbs over the casserole. Bake 30 minutes, or until casserole is hot and bubbly.