Ingredients

• 2 lbs / 900 g yellow or Spanish onions, thinly sliced

• 2 tbsp / 28 g unsalted butter

• 1 tbsp / 15 ml olive oil

• ½ tsp / 3 g kosher salt

• ¼ cup / 60 ml water or beef stock (as needed for deglazing)

Method

1. Heat the Pan: Set a cast iron skillet over medium heat and add the butter and olive oil.

2. Soften Onions: Once the butter is melted and foaming, add the sliced onions. Stir to coat them in the fats and cook for 5–8 minutes until they become translucent.

3. Caramelize: Reduce the heat to medium-low. Continue to cook for 45–60 minutes, stirring every 5–10 minutes to ensure even browning.

4. Deglaze: As a brown glaze (fond) forms on the bottom of the pan, add 1 tbsp of liquid at a time. Scrape the bottom of the pan with a wooden spoon to release the flavor back into the onions. Repeat this process throughout the hour whenever the pan begins to look dark.

5. Season: Once the onions have reached a deep mahogany color and a jammy consistency, stir in the salt and remove from the heat.

6. Serve: Use immediately or store for later use.

Additional Notes

• Patience is Key: This is a lengthy process—trust the timing. Don't get excited and turn up the heat to speed things up; just allow the onions to do their thing.

• Deglazing: You aren't necessarily looking for a ton of fond to form; the main goal is the caramelization of the onions themselves. I only ended up needing about 2 tbsp of beef stock total for the entire process.

• Stirring Frequency: Avoid stirring too frequently. You want the onions to sit on the bottom of the cast iron long enough to actually brown. I found that stirring every 7 minutes worked perfectly.

• Total Time: While the standard range is 45–60 minutes, I ran these for about 65 minutes total to get the right consistency.

• Optional Additions: Since I was making these for a steak sandwich, I considered adding Worcestershire sauce or balsamic vinegar. I kept it basic for this version, but those are great options if you want to experiment with the flavor profile.