Step 1

Preheat the oven to 300°F/148°C and grease a 9-inch removable bottom tart pan.

Step 2

Using a food processor or mixer fitted with the paddle attachment, beat the butter, sugar, vanilla, and brown sugar vigorously until pale and fluffy, about 3 minutes. It's an important step to beat the butter and sugar well together when making shortbread, as this ensures the shortbread is light, crisp, and holds together.

Step 3

In a separate bowl, sift the flour and salt. Add it to the butter mixture and mix until blended (forming large clumps).

Step 4

Transfer the mixture to the pan and press it evenly around the base and sides. Use a fork to dock the bottom of the dough all over.

Step 5

Cover with plastic wrap and allow the dough to rest for at least 30 minutes.

Step 6

If using a filling that needs to bake in the crust, partially bake the crust for 15 minutes, then fill and bake as directed. If you're using it for a shell, bake for 45 minutes or until the edges are lightly browned.

Step 7

Cool completely in the pan on a cooling rack before pressing the bottom of the pan up through the middle and gently remove it from the pan before filling.