Melted Fennel Gratin

Preparation

1. Step 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.

   Step 2

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

   Step 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.

   Step 4

   Cover pan; cook, stirring occasionally and adjusting heat as needed to ensure mixture stays at a gentle simmer, until fennel is very tender, 15–20 minutes.

   Step 5

   Heat broiler (place a rack in upper third if broiler is in the oven). Uncover fennel on stovetop and increase heat to medium-high. Add ½ cup heavy cream and cook, stirring occasionally, until cream reduces so all of sauce is clinging to fennel, about 5 minutes. Taste and season with more salt and pepper if needed (keeping in mind that the Parmesan is coming and it will add a lot of saltiness).

   Step 6

   Scatter 2 oz. Parmesan, finely grated (about 1½ cups), evenly over fennel mixture; broil until cheese is melted and golden, about 5 minutes (watch it closely). Top gratin with reserved fennel fronds to serve.