Place a large pan over medium heat. Add the jalapeños. Let them cook for 6-8 minutes, stirring occasionally, or until lightly charred all over. Do the same for the serranos. Remove them from the heat and set them aside.
Add the vegetable oil to the pan and let it heat for 1 to 2 minutes. Raise the heat to medium-high. Add the onions and cook them for 5 to 6 minutes, until soft and fragrant. Stir in the garlic and let everything cook for another minute. Reduce the heat to low, stirring occasionally, as you continue with the next step.
Use a sharp knife to carefully slice the chiles into 1/2-1" pieces. Fold them into the onions. Bring the heat back up to medium.
Add the black pepper, lime juice, Maggi seasoning sauce, Worcestershire, and light soy sauce. Stir well and use a wooden spoon, or silicone spatula, to gently scrape the bottom of the pan and remove any browned bits.
Let everything simmer for 2-3 minutes and then remove it from the heat. Set it aside and serve with your favorite tacos or steak.
Storage: Refrigerate any leftovers in an airtight container for up to 5 days. Keep them away from the heat and sunlight when on the counter for reheating and serving. Reheat: They can be served at room temperature or warm. You can reheat them in the microwave for about 20-30 seconds or in a pan over medium heat for 2-3 minutes.Reduce the heat. Reduce the serranos, or swap them out completely for jalapeños, if you’re not a fan of super spicy condiments.Make them saucy. Double the sauces (soy sauce, Maggi, and Worcestershire) in the recipe, but don’t let them evaporate too much. This will give you plenty of leftover cooking juices, that you can spoon over the tacos, when you serve them with the chiles.Use lemons. Although the flavor might not be as bright, lemon juice will add enough tang to your chiles if that’s all you’ve got on hand.Leave chiles whole for more heat. If you’re a fan of extra spicy food, don’t remove the stems from the chiles and don’t slice them either. Prepare this recipe with whole chiles for some true heat.