3 tablespoons olive oil
1 yellow onion, peeled and thinly sliced
2 garlic cloves, thinly sliced
1 large bunch/1 1/2 pounds Swiss chard, stems and leaves separated and chopped (about 9 cups)
½ teaspoon salt, plus more as needed
⅓ cup half-and-half or heavy cream
8 large eggs
¼ teaspoon black pepper, plus more as needed
3 ounces cotija cheese or queso fresco, crumbled (about 3/4 cup)
1 avocado, sliced, for serving
1 small jalapeño, thinly sliced, for serving
Chopped cilantro, for serving
Smoked hot sauce, for serving
Corn tortillas, toasted, for serving
1 lime, cut into wedges, for serving
Heat oil in a large cast-iron skillet over medium-low heat. Add onion and cook until softening, 5 minutes. Add the garlic and cook until fragrant, 5 minutes more.
Raise the heat to medium-high, add the chard stems, and cook to release some liquid, 5 minutes. Add the chard leaves, in batches, adding more as they wilt, and continue cooking, stirring occasionally, until completely wilted, 3 to 5 minutes more. Season with 1/2 teaspoon salt, pour in the half-and-half and stir loosely together.
Make eight small hollows in the cooked chard with the back of a spoon. Gently crack an egg into each hollow. Cover with a lid or foil and cook on medium-low until the eggs are just set, but still soft, about 7 to 9 minutes. Remove the lid, sprinkle with salt, pepper, cotija, avocado, jalapeño and cilantro. Serve with smoked hot sauce, toasted tortillas and lime wedges.