Belgian Endive Tarte Tatin
8 tablespoons salted butter, plus more for the pan
1 3/4 cups sugar
1 teaspoon vanilla bean paste
1 1/2 lbs (about 6 heads) Belgian endive, ends trimmed and halved*
2 tablespoons lemon juice
1 sheet (about 1/2 lb) puff pastry, thawed if frozen and corners trimmed off
1 egg, lightly beaten with 2 teaspoons water (for eggwash)
Preheat oven to 350F.
Heat a 12-inch cast iron skillet over medium to medium-high heat; add the butter and once melted, add the sugar and the vanilla. Cook, stirring occasionally, until the sugar melts and turns amber in color (see my post on making homemade caramel for more explanation).
Lay the endive halves in the caramel cut side down, tightly packing so they all fit in the pan; sprinkle on the lemon juice. Bake (covered) 20 minutes, then flip each endive over and bake (uncovered) another 20 minutes, or until the endive is very tender.
Turn oven up to 400F and butter a 9-inch ovenproof skillet. Decoratively arrange the endive in the bottom of the buttered skillet. Boil the caramel sauce for a few minutes until it’s reduced to about the thickness of cough syrup (the endive will have given off quite a bit of water); taste and add additional sugar as desired, heating and stirring to fully dissolve any added sugar. Add 3/4 cup of the caramel sauce (reserving the extra sauce to serve with the tarte) to the pan with the endive, then place the trimmed puff pastry on top and tuck in any edges with a paring knife. Lightly brush the puff pastry with eggwash and cut 4 slits in the pastry so steam can vent.
Bake until the pastry is puffed and golden, about 20 to 25 minutes. Cool about 10 minutes before inverting the tarte onto a plate and serving. Serve with the reserved caramel sauce to drizzle on top, along with a dollop of whipped crème fraîche, whipped cream, or vanilla bean ice cream.