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The Ultimate Slow-Cooked Caramelized Onions: A Base Recipe & Flavor Guide

A close-up of a mound of rich, dark brown caramelized onions piled high on a small white plate.
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Learn the fundamental technique for making deeply caramelized onions. This simple recipe draws out the natural sugars, creating sweet, golden, tender onions perfect for burgers, pasta, or sandwiches.

Ingredients

Scale
  • 3 large yellow onions, thinly sliced
  • 2 tablespoons unsalted butter
  • 1 tablespoon olive oil
  • 1/2 teaspoon salt
  • 1/4 teaspoon sugar (optional, for faster browning)

Instructions

  1. Slice the onions thinly and uniformly. Uniform slices help them cook evenly.
  2. Combine the butter and olive oil in a large, heavy-bottomed skillet or Dutch oven over medium-low heat.
  3. Add the sliced onions and salt to the skillet. Stir to coat the onions completely with the fat.
  4. Cook the onions uncovered for 15 minutes, stirring occasionally, until they soften and release moisture. Keep the heat low to prevent burning.
  5. Reduce the heat to low. Continue cooking for 45 to 60 minutes, stirring every 5 to 10 minutes. The goal is slow cooking to develop deep flavor.
  6. If the onions start sticking too much or browning too quickly, add one tablespoon of water to the pan and scrape up the browned bits (deglazing).
  7. Continue cooking until the onions reach a deep, rich, mahogany brown color and are jammy in texture. If using, stir in the optional sugar during the last 10 minutes.
  8. Remove from heat. These caramelized onions are now ready to use as a savory onion topping or versatile onion ingredient.

Notes

  • For faster results, you can add a pinch of sugar, but true caramelization relies on time, not just sugar.
  • If you are making a large batch, use a wider pan to ensure the onions cook in a single layer, which promotes even browning.
  • These make excellent make ahead savory bases; store cooled onions in an airtight container in the refrigerator for up to one week.

Nutrition

Find it online: https://littlekitchendiary.com/caramelized-onions-base-recipe-technique/