Caramelized Onion with beef

3 large onions , peeled, halved and sliced in the food processor 2 tablespoons butter 2 tablespoons olive oil 6 garlic cloves , sliced 1 teaspoon pepper 1[...]

1 tablespoon olive oil 8 cups sliced yellow onions (about 2 lbs) 5 cups sliced shiitake mushroom caps (about 10 oz whole mushrooms) 4 garlic cloves , minced 2[...]