5 fresh serrano or 10 jalapeño chilies, stemmed (optional: add seeds for heat)
3 whole garlic cloves, peeled
1 large white onion, peeled and sliced 1¼ cm (½ in) thick
60 ml (2 fl oz) olive oil
Coarse sea salt
50 g (2 oz) chopped fresh coriander
Freshly ground black pepper
Preheat the grill. Remove the husks from the tomatillos and rinse the tomatillos under warm water to remove the stickiness. Dry them with a paper towel.
Place the tomatillos, chilies, garlic, and onion on a baking sheet. Drizzle them with the olive oil and sprinkle with 10 ml (2 tsp) of coarse sea salt. Grill them a few inches from the heat, turning everything once, until the tomatillos are softened and slightly charred, about 7 minutes.
Let the vegetables cool to room temperature. Transfer them to a blender with the coriander and puree until smooth. Season with salt and pepper to taste. Store in an airtight container in the refrigerator for up to a week or freeze for up to 2 months.