This delicious hot onion dip combines caramelized onions with old cheddar cheese and a bit of mayo, for a fabulous dip that channels all the great flavours of French onion soup.

warm onion and cheese dip in cast iron skillet with bread

Why you’ll love this hot onion dip recipe

  • Caramelized onions! Yes, they take a bit of extra time, but they are so worth it!
  • This dip uses just 3 main ingredients – onion, cheese and mayo, so it’s easy to make.
  • The caramelized onions together with the melty cheese channels all the best flavours of French Onion Soup.
  • You can assemble this dip ahead, cover and refrigerate it for up to 2 days, so you can bake it later.

Ingredients and substitutions

Sweet Onions – for best results, use sweet onions, such as Vidalia onions. You’ll need 4 cups worth, so you’ll want to start with 2 medium onions.

Green Onions – you’ll use both whole green onions. The white end will be used with the onions and the green tops both in the dip and as a garnish to serve.

Aged or Extra OId Cheddar Cheese – I used a 2-year-old aged white cheddar (Balderson’s), but any good aged white cheddar would work just fine

Mayonnaise – I used Hellman’s, but you can use what you have or regularly use.

Step-by-step photos

  1. Cut up the onion and garlic, then add salt and sugar to the onion mixture.
  2. Add butter and oil to a skillet and heat. Add onion mixture to the skillet.
  3. Cook the onions over medium heat for 5 minutes, then reduce heat to medium-low and cook, stirring regularly for another 25-30 minutes.
  4. Cook onions just until they are starting to caramelize and are a light golden colour.
  5. Add the caramelized onions to a bowl. Add the shredded cheddar cheese, green onion and mayonnaise and stir to combine (sorry, I somehow missed taking a photo of the end of that part of the process).
  6. Spoon into a baking dish, cover and refrigerate until cold, about I hour. Bake immediately or keep refrigerated for up to 2 days to bake later.

Recipe video

Recipe tips!

  • Once the dip is assembled, you’ll need to cover and refrigerate the dip until it is cold before baking, which is about 1 hour. Don’t forget to factor in this extra chilling time.
  • There is a lot of fat in this dish, both with the onions and of course, the cheese. It can sometimes pool a bit on the top of the dip after baking. If that happens, I like to use a piece of soft bread to “blot up” and remove any oil before serving.
  • This is quite a heavy dip, so I like to serve it with toasted bread or sturdy crackers or vegetables.
hot onion dip in cast iron skillet

Making ahead, storing and re-heating

This onion dip is best enjoyed freshly baked and served warm. You can assemble the dish ahead, cover and refrigerate up to 3 days, to bake and enjoy later.

Refrigerate any leftovers well-covered, for several days. This dip will firm up when refrigerated. Re-warm in the microwave or cover with foil in a 350F oven until warmed.

Hot onion dip in cast iron skillet with bread

Get the Recipe: Hot Onion Dip

This delicious hot onion dip combines caramelized onions with old cheddar cheese and a bit of mayo, for a fabulous dip that channels all the great flavours of French onion soup.
5 stars from 1 rating
Prep Time: 15 minutes
Cook Time: 1 hour
Chilling Time:: 1 hour
Total Time: 2 hours 15 minutes
Yield: 24 servings

Ingredients

  • 4 cups sweet onion, such as Vidalia, thinly sliced, from about 1 large onion
  • 3 green onions
  • 1 Tablespoon garlic, minced
  • 1/2 teaspoon salt
  • 1/2 teaspoon white granulated sugar
  • 2 Tablespoons butter
  • 2 Tablespoons cooking oil, vegetable oil or olive oil
  • 3/4 cup mayonnaise
  • 3 cups extra old white cheddar, shredded

For topping:

  • 1/2 cup extra old white cheddar, shredded

For garnish:

  • 2 Tablespoons green onion, diced

Instructions
 

  • Slice the onion in half, then thinly slice. Separate rings and measure out to 4 cups. Slice the white parts of the green onions and add to rings, along with garlic. Sprinkle the onion mixture with the salt and sugar and stir to mix.
  • Heat the butter and oil in a large skillet over medium heat. Add the onion mixture. Cook for 5 minutes, stirring often, then reduce the heat to medium-low. Continue cooking, stirring regularly, until the onions start to caramelize, about 20 to 25 minutes.
  • Remove the cooked onion mixture to a cutting board. Finely chop the onions and place into a large bowl.
  • Thinly slice the green onion tops and set aside 2 Tablespoons for garnish. Add the remaining green onion to the bowl with the cooked onion.
  • Add the mayonnaise to the bowl with the onions. While stirring in the mayonnaise, sprinkle in the shredded cheese and stir until well combined.
  • Spoon the mixture into a shallow ovenproof dish that will hold about 3 cups. Spread evenly. Cover with plastic wrap and refrigerate at least until cold, about 1 hour or up to 2 days.
  • About 30 minutes before serving, heat oven to 375°F. (not fan assisted)
  • Sprinkle the top of the cold onion dip with the remaining shredded cheddar cheese. Place in oven and bake until golden, about 30 to 35 minutes. *If you'd like to brown it up a bit more, switch the oven to broil for a couple of minutes.
  • Tip! Allow the dip to stand at least 5 minutes before serving. If some oil has pooled on top of the dish, use a piece of soft bread to "blot" the oil off before garnishing and serving.
  • To serve, sprinkle with additional diced green onion and serve warm with toasted baguette slices, crackers or vegetables for dipping.
  • Tip! This is a heavy dip, so it's best to toast any bread so it is sturdier.

Notes

Be sure to read the notes above this Recipe Card, for more tips on making this recipe. You’ll also find step-by-step photos and a recipe video that you might find helpful.
Cuisine: American, Canadian
Course: Appetizer
Serving: 1serving, Calories: 103kcal, Carbohydrates: 4g, Protein: 4g, Fat: 8g, Saturated Fat: 4g, Polyunsaturated Fat: 1g, Monounsaturated Fat: 2g, Trans Fat: 0.04g, Cholesterol: 20mg, Sodium: 229mg, Potassium: 55mg, Fiber: 0.5g, Sugar: 2g, Vitamin A: 220IU, Vitamin C: 2mg, Calcium: 125mg, Iron: 0.1mg
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