Step 1

Preheat the oven to 375 degrees F. Grease a 9x13 rectangular baking dish and set aside.

Step 2

Place the sliced potatoes in a large pot and cover with salted water. Make sure you cover the potatoes by at least a couple of inches, so that there is room in the pot for the cauliflower to cook too. Bring the pot with the potatoes to a boil, add in the cauliflower florets, and cook for 8 to 10 minutes until the potatoes are soft but not falling apart. Drain.

Step 3

While the veggies are cooking, melt the butter in a saucepan over medium heat. Whisk in the flour to form a paste. Slowly pour in the milk followed by the broth, whisking constantly. Cook for a few more minutes, whisking often, until the sauce thickens. Stir in the Dijon mustard, onion powder, garlic powder, salt, and pepper.

Step 4

Turn off the heat on the sauce. Stir the parmesan cheese and ¾ cup of the cheddar cheese into the sauce.

Step 5

Transfer the cooked veggies to the greased baking dish and spread out in an even layer. Pour the cheese sauce over the veggies.

Step 6

Sprinkle the casserole with the rest of the cheddar cheese and the sliced chives. I like to use kitchen shears to quickly cut the chives over the casserole.

Step 7

Bake for 20 to 25 minutes until the sauce is bubbling and the cheese is slightly browned. Flip the broiler on and finish baking the dish for 2 to 3 more minutes until the cheese is fully browned.

Step 8

Remove from the oven and garnish with more fresh chives as desired. Let it sit for 5 to 10 minutes before serving.

Step 9

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