Preheat the oven to 350 degrees F (175 degrees C).

Combine tomatillos, serrano peppers, and garlic in a bowl. Drizzle with olive oil and toss to coat. Transfer to a baking sheet.

Place in the preheated oven and roast until tender, about 30 minutes. Remove vegetables from oven, cool slightly, and transfer to the bowl of a food processor. Puree until smooth.

Reduce oven temperature to 275 degrees F (135 degrees C).

Heat lard in a Dutch oven or heavy oven-safe pot over medium-high heat. Sprinkle pork with garlic salt and pepper and add to the pot in batches. Cook each batch until browned, about 7 minutes, removing to a plate with a slotted spoon. Drain and discard all but 2 tablespoons pan drippings.

Add onion and bell pepper to the pot. Sauté, stirring occasionally, until onion has softened and turned translucent, about 5 minutes.

Pour wine into the pan and bring to a boil while scraping the browned bits of food off the bottom of the pan with a wooden spoon.

Stir in browned pork, tomatillo puree, chicken stock, cilantro, oregano, cumin, and salt.