Preheat the oven to 400 degrees F.

In a food processor or chopper, pulse the walnuts until the are finely chopped, and the pieces are about the size of breadcrumbs.

Place the chopped nuts in a large bowl and add the remaining ingredients, tossing together with a fork.

Press the mixture evenly over the bottom and up the sides of a 9-inch tart pan with a removable bottom.

Bake for 15 minutes.

Pour the milk into a small pot and place over medium heat until small bubbles form around the edges.

In a medium mixing bowl, whisk the egg yolks with the maple syrup, cornstarch, and salt.

Slowly pour the hot milk over the egg mixture, while whisking, to warm the eggs.

Place the mixture back into the pot and place over low heat. Cook, stirring constantly, until the mixture comes to a bubble and becomes very thick.

Stir in the vanilla and transfer to a heat safe container. Lay plastic wrap over the surface. Chill for 2 hours.

Spread the maple custard in the walnut tart shell.

Warm the apple slices in the microwave until pliable.

Roll a slice of apple into a tight spiral and stand it up vertically in the custard. Continue to arrange apple slices in a concentric pattern, around the first one, building a rose pattern.

Warm the apricot jam, and thin it with lemon juice. Brush this glaze over the apples, for shine and to prevent browning (optional).