Step 1

Start by heating the 3 tablespoons of vegetable oil in a pan over medium-high heat. Add the minced onion and let this cook, stirring often, until the onion has nicely browned. Turn off the heat and set aside when it's ready.

Step 2

If you are starting from fresh peppers, you will need to roast, peel and deseed them. This is a good tutorial on that, or you can use canned or pre-frozen roasted chiles.

Step 3

Add all the ingredients for the mayo and puree. Add salt to taste. You will have some left over, so keep it in a container in the fridge, where it will last a couple weeks.

Step 4

Mix the ground meats together and knead well so they combine cohesively. Form into balls and slightly flatten them. If you are grilling, just form normal patties and grill. What follows is for a smashburger.

Step 5

Get a comal or griddle or large frying pan hot. Add the 1 tablespoon of vegetable oil. Set one of the balls of meat in the center of the oil, and use it to spread the oil around a little. Slick the underside of a bacon press or other pan with some oil. Press the meat into a patty of about 1/2 inch thick, more or less. Hold the pressure for about 30 seconds, then slide the bacon press off the patty to the side. Don't lift straight up or the patty will break. Salt the patty as it cooks.

Step 6

Let the meat cook for about 90 seconds more, then flip. Salt the other side. Add some onions to the middle of the patty and top with a slice of cheese. I like to put a metal bowl over the burger now to melt the cheese. Let this sit for another minute to 2 minutes, depending on how well cooked you like your burgers. While this is happening, lay the lettuce leaves on your buns and top with a little of the mayo.

Step 7

To build the burger, set the patty on the bun, then top with some of the roasted chiles and some more mayo. Serve at once. You can also layer like this: patty, onions, green chiles, then cheese. The greenery always touches the bun, and the mayo or other sauce goes on between lettuce and burger. °