Bring 6 cups of water to a rolling boil in a large pot and add 1/2 teaspoon kosher salt. Add the haricot vert and blanch for 2 minutes until bright green and just tender-crisp. Immediately transfer to a bowl of ice water (using a slotted spoon) to stop cooking. Let cool 2–3 minutes, then drain and pat dry.

Render bacon

While the beans blanch, place the diced bacon in a cold skillet and set over medium heat. Cook, stirring occasionally, until fat renders and bacon is crisp but not overly hard, about 6–8 minutes. Remove bacon with a slotted spoon to a paper towel-lined plate, leaving the bacon fat in the pan.

Warm aromatics in butter

To the skillet with the reserved bacon fat, add 1 tablespoon butter and 1 tablespoon olive oil and heat over medium. Add the minced garlic and the chopped smoked chiles and sauté 30–45 seconds until fragrant (don’t let the garlic brown).

Sauté haricot vert

Add the blanched and drained haricot vert to the skillet. Increase heat to medium-high and sauté, tossing frequently, for 2–3 minutes until the beans are heated through and gain a little color. Season with the remaining 1/2 teaspoon kosher salt and 1/2 teaspoon freshly ground black pepper.

Finish with butter, bacon, lime, cilantro

Turn off the heat and add the remaining 1 tablespoon butter, the crisped bacon, and the lime juice. Toss gently to coat so the butter melts and the lime and bacon distribute evenly. Stir in the chopped cilantro.

Plate and top with cotija

Transfer the haricot vert to a serving dish. Sprinkle the crumbled cotija evenly over the top and finish with a light crack of black pepper and, if desired, an extra pinch of chopped smoked chile for heat and smoky flavor. Serve immediately.