Spatchcock the chicken:

Place chicken breast-side down on cutting board. Cut along both sides of the backbone with a sharp, heavy knife or kitchen shears. Remove and reserve the backbone for stock if desired. Press down on breastbone with palms until you hear it crack and chicken is as flat as possible. Using shears or knife, cut right through the breast following the crack if possible. If necessary, cover the top edge of the knife with several layers of towel to protect it and use a kitchen/meat mallet to assist getting through. (At your own risk and use good judgment.)

Loosen skin from breasts and thighs, being careful not to tear the skin and to leave it attached as much as possible. Set aside.

Mix together marinade:

In a large bowl, add the garlic, soy sauce, aji Amarillo (or substitute), lime juice, paprika, cumin, pepper, and salt. Add the chicken and turn to coat, working some of the marinade up under the skin. Cover and refrigerate at least 2 hours and up to 12 hours, maybe longer if desired.

Cooking:

When ready to cook, preheat oven to 450 degrees F. Transfer chicken, skin side up on to a heavy sheet tray. Drizzle with oil. Roast until skin is golden and chicken is cooked through, 35 to 45 minutes (if using chicken parts, remove the breasts after 25 to 35 minutes). Safe temperature should be 165 degrees F. so remove at 160 and the temperature will rise as it rests. Let sit, loosely covered with foil, for 10 minutes before serving.

Make the Green Sauce:

In a blender, blend onion, garlic, jalapeno, cilantro, vinegar, and egg yolk until very smooth. With the motor running, slowly drizzle in oil until mixture is emulsified. Taste and adjust the seasonings. Thin with a little water if desired.