Start by preparing the tart crust. Unroll the puff pastry sheet onto parchment paper and gently roll it out a bit with a rolling pin. Use a pizza cutter to cut two strips the length of the pastry and two shorter strips for the width. Place these strips on the edges of the pastry to form a raised border.

Beat the egg and brush it over the entire pastry. Use a fork to prick the center (not the edges) to prevent it from puffing up too much.

Preheat the oven to 350°F (175°C) and bake for about 15 minutes, or until the pastry is golden brown. Set aside.

To make the Baileys cream: Pour the milk into a saucepan with 2 tablespoons (30 g) of the sugar and heat gently.

While the milk is heating, in a separate bowl, combine the cornstarch, whole egg, egg yolk, remaining sugar, and salt. Whisk well.

When the milk starts to steam, slowly pour it into the cornstarch mixture, whisking constantly.

Return the mixture to the saucepan and cook over low heat, stirring constantly, until it just starts to boil and thickens.

Remove from heat and add the butter and Baileys. Mix well. (I only added 1 1/2 tablespoons of Baileys, but after tasting the tart, I would use 2 or 3 tablespoons—adjust to your taste.)

Let the cream cool completely, then spread it over the baked puff pastry crust using a spatula or spoon.
Top with chocolate balls, dust with powdered sugar, and garnish with mint leaves.