Prepare the tart crust by mixing flour, sugar, orange zest, and salt in a bowl.

Add cold butter and mix until crumbly.

Incorporate egg and heavy cream until the dough just comes together.

If needed, add more cream to hydrate the dough.

Shape the dough into a disk, wrap in plastic, and refrigerate for at least 1 hour.

Make the pumpkin filling by combining pumpkin, eggs, sugar, flour, spices, and salt in a bowl.

Whisk in heavy cream and bourbon.

Prepare the streusel topping by pulsing flour, sugar, cinnamon, and salt in a food processor.

Add cold butter and pulse until crumbly.

Stir in toasted walnuts and crystallized ginger.

Preheat oven to 350 degrees F.

Roll out the chilled tart dough into a 13-inch round.

Drape the dough into a 10-inch tart pan, fitting it into the contours.

Fold excess dough to create an edge.

Pour the pumpkin mixture into the unbaked tart crust.

Scatter the streusel mixture evenly over the filling.

Bake for 50-65 minutes, until the topping is cooked and the center is set.

Cool the tart on a rack for at least 2 hours before serving.