Heat the butter and olive oil in a heavy-bottomed pot or pan set over medium-high heat. Peel and slice the onions into rounds while the butter is melting and add them to the pot. Toss to coat the onions and season with salt and pepper, to taste. Turn the heat down to medium and do not cover the pot. You want these babies to get brown! Stir occasionally, for about 10 to 15 minutes, then turn the heat to medium-low. Keep stirring (switch to a spatula or wooden spoon to scrape up the browned bits) until the onions are browned and soft. Add the thyme leaves, toss and remove from the heat. These will keep for 5 days in a covered bowl in the refrigerator. Use the leftovers with eggs, on top of a salad, or straight from the bowl with a fork.
This recipe was provided by a chef, restaurant or culinary professional. It has not been tested for home use.