4.5 lb. yellow onions, sliced
6 T. olive oil
1 T. crushed red pepper flakes
12 ciabetta rolls
Aioli (1.5 c olive oil, 3 T. white wine vinegar, 6 medium garlic cloves, dash of salt; process until blended and slightly thickened. Add freshly ground black pepper to taste)
3 c. basil leaves
3 c. roasted red pepper strips
1.5 lb. sharp white cheddar, sliced
1.5 c. pitted Kalamata olives, halved
6 oz. prosciutto or pancetta, cut in paper-thin slices (optional, don't use if wanting sandwich to be vegetarian)
Caramelize onions over low heat in oil for 15 to 20 minutes, or until golden; mix in red pepper flakes.
Split a ciabetta roll and lightly brush the inside with aioli.
For each serving, layer the bottom of the roll with 1/4 c. basil leaves, 3/4 c. caramelized onions, 1/4 c. roasted red pepper, 2 oz. cheese and 2 T. olives. Add 1/2 oz. prosciutto if desired. Brush the top of the roll with aioli.
Place in a panini grill set at medium-high and slowly close the lid, somewhat flattening the sandwich inside. Grill 15 minutes or until the sandwich is golden and the cheese is melted.