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Cauliflower and Leek Au Gratin

I am a recent addition to the world of stay-at-home moms. I have four children and have decided to homeschool them. It's an adventure!

What to Do With Leeks?

We have been participating in a local Food Co-Op and have enjoyed a basket full of fresh vegetables and fruit each week. The basket is always pre-ordered, and the specifics of the content is unknown until Monday night before a Tuesday pick-up. The result? Each basket is like a miniature surprise full of yummy food that I may or may not be familiar with cooking.

The surprise this week is leeks. I am partially convinced that these are green onions on steroids, but I'm game to try some new recipes. The only dishes that I've ever heard of with leeks were soups, and I am determined to start my adventure with something different. I've landed on an adaptation of leek and potato au gratin. I don't have potatoes, but I do have cauliflower—so let's try this.



What Does Au Gratin Mean?

Au gratin refers to a dish that has been sprinkled with bread crumbs and cheese, then browned. It is common in many recipes to leave off the bread crumbs (as we will do here), but they are an optional add-in when you sprinkle on the mozzarella at the end.

A vegetable gratin is a good way to slip vegetables to my kids with a sauce that encourages them to actually eat them. Adding the leeks could be a game changer (you know, that fear of all things green), but I have hopes that we can pull this off. So, let's get cooking!

Cook Time

Prep timeCook timeReady inYields

20 min

50 min

1 hour 10 min

8 servings


  • 1 head cauliflower, sliced
  • 1 head leeks, chopped
  • 1/2 medium yellow onion, chopped
  • 1/2 cup butter
  • 1 tablespoon coconut oil
  • 1 tablespoon minced garlic
  • 1 teaspoon bay leaves
  • 2 sprigs thyme
  • 1/4 teaspoon nutmeg
  • 3/4 cup 2% milk
  • 1 cup shredded mozzarella cheese
  • 1 cup bread crumbs, optional


Step 1: Prepare Your Ingredients and Equipment

  1. Preheat your oven to 350°F.
  2. Slice up one head of cauliflower into something akin to the potato rounds that are used in potato au gratin.
  3. Grease a 9x12-inch baking pan and layer your slices of cauliflower along the bottom of the pan. Sprinkle it liberally with salt and pepper.
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Step 2: Cook the Vegetables

  1. Melt 2 tablespoons of butter and 1 tablespoon of coconut oil in a large sauce pan. Chop up the leeks and onions and add them to the pan.
  2. Drop in 2 sprigs of fresh thyme and stir on medium heat for about 5 minutes or until the onions are clear and the leeks are soft.
  3. Discard the thyme. Spread the mixture over the top of the cauliflower.

Step 3: Make the Sauce and Bake the Dish

  1. Melt 1/4 cup of butter in your empty sauce pan, then mix in the flour until smooth.
  2. Add the minced garlic, milk, and bay to the pan and stir together. Simmer on medium heat for about 5 minutes until the mixture thickens to about the consistency of cream gravy. Stir regularly to prevent the flour from sticking to the bottom and burning.
  3. Add the nutmeg, mix, and pour over the top of the cauliflower and leeks.
  4. Sprinkle the mozzarella over the top and cover with aluminum foil. You may add the bread crumbs with the mozzarella if you would like to make this a traditional au gratin.
  5. Bake at 350°F for about 40 minutes. Uncover and bake another 10 minutes until the cheese is bubbly.

Photo Tutorial

Layer the sliced cauliflower in the pan and sprinkle with salt and pepper.

Layer the sliced cauliflower in the pan and sprinkle with salt and pepper.

Cook the leeks and onions.

Cook the leeks and onions.

Add the leeks and onions to the pan.

Add the leeks and onions to the pan.

Pour the sauce over the vegetables.

Pour the sauce over the vegetables.

Top with cheese and bread crumbs (optional), bake, and enjoy!

Top with cheese and bread crumbs (optional), bake, and enjoy!

How It Turned Out

Our cauliflower and leek au gratin was served with roasted chicken and yeast rolls. I was seriously skeptical about how the leeks would color the flavor because they look and smell so much like green onion to me. However, the leeks soaked up the buttery flavor while the cauliflower added texture and consistency. We were very pleasantly surprised and ended up without any leftovers!

Nutritional information was generated using


  • I suggest tossing the cauliflower in olive oil and roasting at 400°F for about 35 minutes before layering. In addition, toss the leeks and garlic in olive oil, salt them, and roast for about 15 minutes before layering on top of the cauliflower. Then proceed with making your sauce. Roasting deepens the flavor of the vegetables and adds a nice crunch to the cauliflower.
  • You could also add ham or chicken and turn this into an all-in-one dinner.
  • The sauce is a basic Béchamel sauce. However, you can substitute 1 cup of heavy whipping cream for the butter and milk in step 3. I find the flavor to be richer by making the sauce.
  • In addition, Gruyere cheese is the most common cheese used to make au gratin, but has a higher calorie count than mozzarella.

How to Make a Basic Béchamel Sauce

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