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Deliciously Cheesy Baked Fennel Onion Gratin Recipe

Fennel Onion Gratin is a deliciously cheesy side dish that is wonderfully flavorful and simple to make. It's the perfect accompaniment to any main course, or it can become the main course all on its own.
Prep Time15 mins
Cook Time30 mins
Total Time45 mins
Course: Vegetable - Side Dish
Servings: 4 cups
Author: Renee - Kudos Kitchen


  • 3 fresh fennel bulbs fronds removed, and cut into (approximately) 1" x ¼" slices
  • 1 medium red onion cut into (approximately) 1" x ¼" slices
  • 3 tablespoons olive oil
  • 2 tablespoons butter
  • teaspoon coarse salt
  • ½ teaspoon black pepper
  • ¼ cup chicken or vegetable broth
  • ¼ cup mayonnaise
  • ½ cup shredded mozzarella cheese
  • ¼ cup shredded Romano cheese


  • Preheat oven to 425 degrees.
  • Melt the oil and butter in a large skillet over medium heat.
  • Add the fennel and onion to the skillet and stir well.
  • Add the salt and pepper to the skillet and cook the fennel and onion, stirring occasionally, for approximately 4-5 minutes.
  • Add the broth to the pan, scraping up any browned bits from the bottom of the pan. Continue cooking over medium heat for an additional 2-3 minutes.
  • Turn off the heat and stir the mayonnaise, mozzarella and Romano cheese to the fennel mixture and stir well to combine.
  • Spray a small 1½ quart casserole dish or gratin dish with olive oil or cooking spray.
  • Spoon the fennel and onion mixture evenly into the dish.
  • Bake the fennel-onion gratin in a preheated oven for 30-35 minutes, or until the gratin is golden and bubbly.
  • Cool slightly before serving.
  • Enjoy!


Tools and equipment:
cutting board
chef's knife
large skillet
measuring cups
wooden spoons
1½ quart casserole dish or gratin dish
olive oil spray or cooking spray