Caramelized Onion without seed dijon

1 tablespoon olive oil 8 cups vertically sliced yellow onion (about 2 pounds) 5 cups sliced shiitake mushroom caps (about 10 ounces whole mushrooms) 4 garlic[...]

1 tablespoon unsalted butter 5 tablespoons olive oil 1 large fennel bulb, trimmed, halved, cored, and sliced crosswise 1/8-inch thick, fronds reserved 1 large[...]