Put a large, heat-proof serving dish in the preheated oven. Have a brown paper bag or covered glass bowl, large enough to hold the peppers.
Put the salt, pepper, granulated garlic, and cumin in a plastic bag. Add the dry chicken breasts and close the bag. Shake to coat the chicken with the spices. Wash and dry the peppers. If you have a grill that is large enough to accommodate all the chicken and the peppers (and garlic) at once, you can put them all on together. Otherwise grill the peppers (and garlic) first, and continue with preparing the peppers while the chicken is grilling. The idea is to grill the chicken about 6 minutes on each side, just until the breasts are cooked through. Don't allow them to get over done and dried out. As soon as they are ready, put them on the heated serving dish, lightly covered with foil. Grill all the peppers and optional garlic, turning them to blacken all sides of the peppers but just cook the garlic until it is soft. When the peppers and garlic are done grilling, put them in a brown paper bag or covered glass bowl until cool enough to handle. I use rubber gloves to peel the jalapenos. Remove and discard the garlic peel, the blackened pepper peel, the seeds, and any of the liquid from the grilled peppers. Chop the peppers into 1/2 inch pieces, mash the optional garlic, and mix in an attractive serving bowl with olive oil.
Serve the chicken either warm or at room temperature with the peppers on the side. If you have used a lot of jalapenos, this can be quite spicy, so warn your guests!