Step 1. Lightly crush the chicharrones with your hand or a kitchen mallet (do not grind to powder).
Step 2. In a skillet with oil, sauté the onion, garlic, chili pepper, Del Rancho Chicharrones, quesillo, salt, and pepper. Mix well and set aside.
Step 3. In another bowl, prepare the dough by adding the flour, salt, and the remaining 3 cups of water. Knead until firm, smooth, and not sticky.
Step 4. Take a portion of dough, form a ball, and make a hole in the center.
Step 5. Add 1 ½ tablespoons of the chicharrón and cheese filling, then shape into an oval with your hands.
Step 6. Place the pupusa on a preheated griddle over medium heat and cook on both sides.
Step 7. Repeat the process with the remaining dough.
Step 8. Serve hot with any sauce.