Peruvian-style pollo a la brasa, or rotisserie chicken, often comes with intriguing little containers filled with various colorful sauces. One of the sauces is typically bright yellow and spicy, made with the fruity aji amarillo chile pepper. Often there is a mysterious green salsa as well, with a unique mint-like flavor that can be difficult for North Americans to identify.
The secret ingredient in that special green sauce is the Andean herb known as huacatay (wah-ka-tie) or Peruvian black mint. Huacatay is actually from the same genus (Tagetes) as marigolds. Though it's easy to grow, it can be hard to find fresh or dried huacatay in North America. But jarred huacatay paste is often available at Latin markets.
Queso fresco (fresh white cheese), lime juice or vinegar is often added as well. Your favorite pollo a la brasa takeout place probably won't be willing to share their particular recipe, but it's fun to experiment and develop your own special version.
Peel and coarsely chop the garlic. Heat the oil in a small skillet and sauté the garlic over medium-low heat until garlic is fragrant and just starting to turn golden. Remove from heat and let cool in the skillet with the oil.
Coarsely chop the scallions.
Add the garlic and oil to a blender or food processor, along with the scallions. Add the mayonnaise, aji amarillo, huacatay, and cilantro. Process until smooth.
Season with salt and pepper to taste, and add more huacatay or aji amarillo if desired. Keep refrigerated until ready to serve.