Welsh Rarebit With Caramelized Onion Recipe

How much do you know about Wales? With its lyrical language and rolling green hills dotted with sheep, Wales really is a beautiful place. The country's most famous contribution to world cuisine is probably Welsh rarebit, or, to give it its Welsh language name: caws pobi. Although its true origins are questioned, with some claiming that the dish was first created in England, these days it is an undeniable fact that Welsh rarebit is integral to Welsh culture.

So what is Welsh rarebit? This historic dish is sometimes thought of as simply referring to cheese on toast, but to make a proper caws pobi, there is much more to the recipe than simply grilling some cheese on toasted bread. A true Welsh rarebit is made by creating a delicious beer- and cheese-infused sauce that is then broiled on a big chunk of bread. This recipe, developed by Tasting Table's Jennine Rye, adds caramelized onions to the classic caws pobi to create a deliciously decadent dish that is perfect for lunch.

Gather the ingredients for caramelized onion Welsh rarebit

For caramelized onion Welsh rarebit, you'll need onions, olive oil, brown sugar, balsamic vinegar, butter, flour, your favorite ale, mature cheddar cheese, Dijon mustard, and, last but not least, Worcestershire sauce.

With so much focus on the beery-cheesy sauce, it can be easy to overlook the bread. But don't skimp here, as your Welsh rarebit will only be as good as the bread you use. Make sure to pick up something hearty, like sourdough.

As for adaptations, you can easily adjust this recipe to suit a gluten-free diet by picking up some gluten-free bread and flour. Remember to use a gluten-free ale, too.

Caramelize the onions

The first (and very important) step in this Welsh rarebit dish is to make caramelized onions. Using a slow cooking process helps to release the natural sugars in onions, making them deliciously sweet and caramelized — the perfect addition to decadent Welsh rarebit. To do this, you will want to fry the onions in olive oil over a low heat for at least 30 minutes. Keep an eye on them, and if they begin to catch and start sticking to the pan, add a splash of water to keep things moist. Allow plenty of time for this stage to let the onions' natural sugars develop, then add the brown sugar and balsamic vinegar to enhance the sweet and rich flavors even further. Cook for an additional 10 minutes before turning off the heat. 

Make the cheesy beer sauce

Now it's time to start making the creamy sauce. The base of the sauce is a roux, which you'll make by melting the butter in a small saucepan and then whisking in the flour to form a thick paste. Next, slowly add the ale in increments, continuing to whisk the mixture all the while, to keep the sauce nice and smooth. This process is the same basic recipe for making a cheese sauce, except you're swapping the milk for ale.

The resulting mixture with have a lovely deep flavor, with the ale complementing the sharp cheddar. Once all of the ale has been incorporated, it's time to add the grated cheese, Dijon mustard, Worcestershire sauce, and a good amount of black pepper.

Broil the Welsh rarebit

To finish your Welsh rarebit, take the slices of sourdough (or whichever bread you have decided to use), and heap the caramelized onions on top. Add a healthy dollop of the cheese sauce, and then place the bread in the broiler until the top takes on a beautiful golden brown color. Serve straight away while it's all melty and hot, adding extra black pepper and another dash of Worcestershire sauce to taste.

If you enjoyed this recipe and want to try something similar, you can adapt your Welsh rarebit and make it a Buck rarebit by adding an egg.

Caramelized Onion Welsh Rarebit Recipe
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Conquer your day with Welsh rarebit, also known as the world's best cheese toast.
Prep Time
Cook Time
Caramelized onion Welsh rarebit
Total time: 1 hour, 5 minutes
  • 1 tablespoon olive oil
  • 3 medium onions, thinly sliced
  • Salt, to taste
  • 1 tablespoon brown sugar
  • 1 tablespoon balsamic vinegar
  • 4 tablespoons butter
  • ⅓ cup plain flour
  • 1 pint golden ale, warmed
  • 8.5 ounces mature cheddar, grated
  • ½ teaspoon Dijon mustard
  • 1 teaspoon Worcestershire sauce
  • Black pepper, to taste
  • 4 large slices sourdough bread
Optional Ingredients
  • Green salad, for serving
  1. To caramelize the onions, heat a large, heavy-bottomed pan over low heat. Add the olive oil and sliced onions to the pan and allow them to slowly cook for 30 minutes. Stir the onions occasionally, and, if they begin to catch a little, add a splash of water to the pan.
  2. When the onions are very soft, add the brown sugar and balsamic vinegar to the pan and let the onions cook for another 10 minutes, then remove from heat.
  3. To make the cheese sauce, melt the butter in a medium-sized saucepan, and then add the flour. Whisk everything together to form a roux, and then slowly add the ale, whisking well between additions, until a thick, smooth sauce has formed.
  4. Add the grated cheddar cheese to the ale mixture along with the Dijon mustard, Worcestershire sauce, and plenty of black pepper. Once all of the cheese has melted into the sauce, remove the pan from the heat and allow it to cool.
  5. Heat up your grill to medium-high heat (or turn on your oven's broiler). Spread the caramelized onions onto the slices of sourdough bread, then top with spoonfuls of the cheese sauce. Place the bread under the grill or broiler until the tops are golden brown.
  6. Serve straight away, with an extra splash of Worcestershire sauce and a side green salad if desired.
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