1/3 cup olive oil
1 clove garlic, pressed
8 oz. sliced fresh button or portobello mushrooms
1 15 oz. can diced tomatoes
1 tsp. sugar
1/2 tsp. kosher salt
1/4 tsp. coarse ground pepper
1 Tbsp. chopped fresh oregano (1 tsp. dried)
1 Tbsp. chopped fresh basil (1 tsp. dried)
1 large yellow onion
2 lbs. bulk sweet Italian sausage
6 oz. sliced mozzarella cheese
12 large fresh basil leaves (optional)
6 ciabatta or focaccia rolls, split
Prepare a medium-hot fire in a charcoal grill with a cover, or preheat a gas grill to medium-high.
In small bowl, mix garlic with olive oil.
Heat a heavy stainless-steel skillet (NOT cast iron or aluminum) on the grill. When hot, coat bottom of pan with one tablespoon garlic oil; add mushrooms, sauteeing and flipping until mushrooms are golden and caramelized. Stir in diced tomatoes, sugar, salt, pepper, oregano and basil and bring sauce to a boil; cook, stirring frequently, until sauce thickens. Move skillet to cool part of grill.
Cut onion into six equal slices, keeping rings intact. Insert skewers through the sides of each slice to help keep slices whole during grilling. Brush both sides of onion with garlic oil; grill two to three minutes per side or until slighly softened and caramelized. Do not overcook.
Remove from grill and keep warm.
Divide Italian sausage into 6 equal portions. Roll each portion flat between two pieces of plastic wrap in a rectangle slightly larger than a ciabatta roll. Brush each patty on both sides with garlic oil; grill, covered, about 5 minutes on the first side until nicely browned. Flip patties and cook two minutes, covered. Top each pattie with a slice of mozzarella and cover grill. Cook about three minutes longer or until cheese is melted and sausage is cooked through. Remove from grill and keep warm.
Brush cut sides of ciabatta rolls with remaining garlic oil. Grill, cut sides down, until golden.
To serve, place bottom of roll on plate and cover with a spoonful of sauce, top with a sausage patty, an onion slice with skewer removed, another spoonful of sauce, two basil leaves and the top of the roll.