Caramelized Onion and Fennel Crostini

2 tablespoons olive oil plus extra for brushing phyllo sheets 2 cloves garlic freshly minced 3 each red onions halved and thinly sliced 1 each yellow onion[...]

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[...]