Melted Fennel Gratin

Instructions

1. Melt 4 Tbsp. unsalted butter in a large cast-iron skillet (about 12") or braiser over medium heat. Add 1 large white onion, thinly sliced through root end, 6 garlic cloves, coarsely chopped, and a large pinch of kosher salt and cook, stirring occasionally, until onion is translucent, 6–8 minutes.

2. Meanwhile, halve 4 medium fennel bulbs, trimmed, some fronds reserved, through root ends; thinly slice lengthwise about ¼" thick.

3. Add 4 small dried bay leaves, 1½ cups low-sodium chicken or vegetable broth, ½ cup dry white wine, 2 tsp. freshly ground pepper, and a few large pinches of kosher salt to onion mixture. Stir to combine, then add fennel (pan will be very full) and cook, occasionally turning fennel with a heatproof rubber spatula, until broth is simmering and fennel has reduced in volume slightly, 6–8 minutes.