1. Prepare the Shortcrust Pastry

1. Combine Dry Ingredients: In a large mixing bowl, combine the plain flour, caster sugar, and a pinch of salt.
2. Rub in the Butter: Add the cold, cubed butter to the flour mixture. Using your fingertips, rub the butter into the flour until the mixture resembles fine breadcrumbs.
3. Add Egg Yolk and Water: Make a well in the center of the mixture and add the egg yolk and cold water, one tablespoon at a time. Mix gently until the dough begins to come together.
4. Form the Dough: Gather the dough into a ball, flatten it into a disc, wrap it in cling film, and refrigerate for at least 30 minutes.

2. Preheat the Oven

Preheat your oven to 180°C (160°C fan)/350°F/gas mark 4.

3. Roll Out the Pastry

1. Roll the Dough: On a lightly floured surface, roll out the chilled pastry dough to fit a 23cm (9-inch) tart tin. Ensure the dough is slightly larger than the tin.
2. Line the Tart Tin: Carefully transfer the rolled pastry into the tart tin, pressing it into the edges and trimming any excess. Use a fork to prick the base lightly.

4. Blind Bake the Pastry

1. Prepare for Blind Baking: Line the pastry with baking parchment and fill it with baking beans or rice.
2. Bake the Crust: Place the tart tin in the preheated oven and bake for 15 minutes. Remove the parchment and beans, then bake for an additional 5 minutes until the crust is lightly golden. Remove from the oven and set aside.

5. Make the Custard Filling

1. Whisk Eggs and Sugar: In a mixing bowl, whisk together the whole eggs and caster sugar until well combined.
2. Heat the Milk: In a saucepan, gently heat the milk until it is just about to simmer. Do not let it boil.
3. Combine and Temper: Slowly pour the warm milk into the egg mixture while continuously whisking to prevent the eggs from scrambling.
4. Add Vanilla: Stir in the vanilla extract.
5. Strain the Custard: Pour the mixture through a fine sieve into a clean bowl to ensure a smooth custard.

6. Assemble and Bake the Tart

1. Fill the Pastry Shell: Pour the custard mixture into the blind-baked tart shell, spreading it evenly with a spatula.
2. Bake the Tart: Return the tart to the oven and bake for 25-30 minutes, or until the custard is set but still slightly wobbly in the center.
3. Cool the Tart: Remove the tart from the oven and allow it to cool completely in the tin on a wire rack.

7. Serve the Tart

1. Garnish: Once cooled, sprinkle freshly grated nutmeg over the top for added flavor.
2. Slice and Serve: Carefully remove the tart from the tin, slice, and serve. Optionally, dust with icing sugar before serving.