To make Mexican Salsa Verde:
Whirl garlic in a food processor until finely chopped. Add anchovy, capers, lime zest and lime juice. Pulse in olive oil just until combined. Add tomatillos, parsley and cilantro. Pulse just until slightly chunky, but not pureed. Use immediately or refrigerate in a sealed jar for up to 2 weeks.
To make BBQ-Chicken Tostadas:
Toast 6-in. flour tortillas in a non-stick pan until brown and crispy on both sides, 1 to 2 min per side. Top each tortilla with 1/2 cup sliced BBQ chicken, then sprinkle with thinly sliced fresh chilies, chopped cilantro and a squeeze of fresh lime (to taste). Drizzle with Mexican Salsa Verde.