Bring butter to room temperature.

Mix unsalted butter and salt in a bowl until soft. Gradually add granulated sugar (for tart dough) in two portions, mixing each time. Add egg yolk and mix, then sift in cake flour and combine into a dough. Wrap in plastic and refrigerate for 1 hour.

Grease the tart mold with butter (extra amount) and lightly dust with cake flour (extra amount).

Roll out the dough between plastic wrap into a circle and press into the mold. Poke holes in the base with a fork and wrap in plastic. Refrigerate for 20 minutes.

Preheat the oven to 170°C and bake the tart shell for 15 minutes.

Cut pumpkin into bite-sized pieces and microwave in a heatproof container at 600W for 4 minutes. Mash while hot, sieve, and let cool.

Mix mashed pumpkin with granulated sugar and egg yolk, combining each time. Add heavy cream and vanilla oil, mixing thoroughly.