Heat the olive oil in a large skillet over medium-high heat.
Once hot, add the tomatillos, jalapeños, serrano, if using, onion, and unpeeled garlic cloves. Cook for 10–15 minutes, turning occasionally, until everything is softened, blistered, and deeply charred on all sides.
Let the vegetables cool slightly, then peel the garlic and transfer everything to a blender.
Add the cilantro, lime juice, drained pickles, and ¼ cup of the reserved pickle juice. Blend until the salsa reaches your desired consistency, adding more pickle juice as needed.
Taste and adjust with more pickle juice or lime juice as needed.
Serve immediately with tortilla chips, or refrigerate before serving to let the flavors deepen even more.
