Add ½ cup cold, cubed salted butter. Use a pastry cutter or fingertips to work it into coarse crumbs with pea-sized butter pieces.

In a small bowl, mix 1 large egg yolk, 1 ½ tsp white wine vinegar, and 2 tbsp ice water. Stir into flour mixture until dough holds together. Add up to 1 tbsp more water, 1 tsp at a time, if dry.

Form dough into a disk, wrap in plastic wrap, and refrigerate for 30 minutes.

Roll dough to ⅛-inch thickness on a lightly floured surface. Fit into a 9-inch tart pan with a removable bottom, press into edges, and trim excess.

Freeze crust in the pan for 1 hour.

Preheat oven to 350°F (175°C). Prick crust bottom with a fork. Wet parchment, scrunch, dry with a towel, and press into crust. Fill with pie weights or dried beans.

Bake with weights for 18 minutes until edges feel firm and smell toasty. Remove weights and parchment; bake 8–10 minutes until center is dry and firm, with a cocoa aroma. If sticky, bake 1–2 minutes more.

Cool crust completely in the pan (~1–2 hours). Gently push up removable bottom to lift crust from pan. Slide onto a flat, sturdy plate. Check for cracks; if any, brush with melted chocolate to seal.

Place 12 oz 50–55% cacao chocolate chips in a heatproof bowl.

Heat 1 ⅛ cups heavy cream in a saucepan over medium until simmering (no boiling).

Pour hot cream over chocolate chips. Let sit 1–2 minutes, then stir gently until smooth. If needed, place bowl over a double boiler with barely simmering water and stir.

Add 2 tbsp softened salted butter, 1 tsp vanilla extract, and a pinch of sea salt. Stir until glossy.

With the freestanding crust on a stable plate, pour ganache into crust, just below the edge. Smooth the top. Move carefully to avoid cracking.

Set at room temperature for 2–3 hours, or refrigerate for 1–1½ hours until firm.

In a chilled bowl, whip 1 cup cold heavy cream with 2 tbsp powdered sugar, ½ tsp vanilla extract, and ¼ tsp xanthan gum until stiff peaks form.

Pipe or dollop whipped cream onto the set tart.

Slice with a hot, dry knife and serve at room temperature.