Sweet Potato Tarte Tatin

Have ready a 9- or 10-inch ovenproof skillet, preferably cast-iron. Unfold puff pastry; place on a sheet of waxed paper. Using a floured rolling pin, roll out creases in pastry. Roll out until dough is between 1/8- and 1/4-inch thick. Cut dough into a circle that is 1/2-inch larger than diameter of top of skillet; discard scraps. Transfer pastry, still on parchment, to a cookie sheet. Prick dough all over with tines of a fork; refrigerate. Heat oven to 375 degrees F.

Place sugar and water in skillet over medium heat. When sugar is evenly moistened, cook on high, without stirring, until sugar caramelizes and turns a dark amber color, about 8 minutes. Remove from heat and whisk in butter, cane syrup, and vanilla bean seeds.

Arrange sweet potato slices in concentric circles, slightly overlapping, in hot caramel in skillet, pressing potatoes down with back of spatula to compact as tightly as possible. Place skillet over medium heat and cook until caramel is hot and bubbly. Remove pastry from refrigerator and center over sweet potatoes, loosely tucking in any overhang. Lightly brush pastry with beaten egg; sprinkle with 1 tablespoon sugar.

Place skillet in oven and bake 40 minutes, until pastry is puffed and golden. Cover skillet with a large-rimmed serving plate; invert skillet so tart turns out onto serving plate. If any sweet potato slices have stuck to skillet, lift them with a fork and replace on tart. Serve warm with ice cream. Garnish with pumpkin seed brittle, if desired.

To make Pumpkin Seed Brittle: Evenly sprinkle 1/3 cup granulated sugar over bottom of a 10-inch nonstick skillet; place over medium heat. Cook until sugar liquefies and turns an amber color, about 5 minutes. Scatter 1/2 cup toasted pumpkin seeds in caramel and stir with heat-resistant rubber spatula until seeds are completely coated. Pour mixture onto a sheet of nonstick foil and let cool. Break brittle into small pieces for garnish.