In a mixing bowl, use an electric mixer to cream together softened butter and powdered sugar until creamy. Beat in the egg and vanilla extract until combined.

Add in the flour, cinnamon, and ground ginger and mix on low speed until it forms a soft dough.

Turn the dough out onto a piece of plastic wrap and press together with your hands to form a flattened disc shape. Wrap the disc in plastic wrap and chill in the fridge for at least 1 hour until firm or overnight.

Preheat oven to 350°F.

After chilling, let the dough sit at room temperature for 10 minutes before rolling out. On a floured surface, roll out the dough into a sheet about ⅛" thick. 

Carefully lay the dough into a fluted 9" tart pan and press into the bottom and sides of the pan. Don't worry if the dough breaks - it's very soft and forgiving. Press small pieces of dough into any cracks or bald spots if needed. Roll the rolling pin over the top edges of the tart to cut the excess overhanging dough off. 

Use a fork to prick holes into the bottom of the tart dough. Gently press a sheet of aluminum foil on top of the tart dough and fill with pie weights or uncooked rice.

Bake tart shell for 15 minutes. Remove the foil and pie weights and bake for an additional 15-20 minutes or until the edges are golden brown. Let tart shell cool before removing from tart pan.

In a small pot, bring the milk and vanilla extract to a simmer.

Meanwhile, in a large mixing bowl, whisk together the eggs, granulated sugar, and cornstarch until creamy. 

Slowly pour the hot milk into the egg mixture while whisking continuously and vigorously to temper the eggs.

Pour this entire mixture back into the pot and return to the stovetop on medium heat.

Stir constantly until it thickens into a creamy custard consistency, about 8-10 minutes. Stir in one cube of butter at a time until all melted and combined.

Pour the custard into the baked tart shell and smooth the top with an offset spatula or spoon. Chill the tart in the fridge while you prepare the peaches or overnight.

Slice peaches into thin wedges or slices. Arrange peach slices on top of the custard.

In a small bowl, stir together jam and water and use a pastry brush to gently brush over the peaches for a glossy finish.

Let the tart chill in the fridge for at least 1-2 hours for the custard to firm up for best results when cutting into the tart.