In a large bowl, whisk together the flour, powdered sugar, and salt. Cut in the cold butter using a pastry blender or your fingertips until the mixture resembles coarse crumbs. Gradually add the ice water, one tablespoon at a time, mixing until the dough just comes together.

Form the dough into a disc, wrap it in plastic wrap, and chill in the refrigerator for at least 30 minutes.

On a lightly floured surface, roll out the chilled dough to a 12-inch circle. Carefully transfer the dough to a 9-inch tart pan with a removable bottom. Gently press the dough into the bottom and up the sides of the pan. Trim any excess dough from the edges.

Prick the bottom of the crust with a fork. Line the crust with parchment paper and fill it with pie weights or dried beans. Bake in a preheated oven at 375°F (190°C) for 20 minutes. Remove the parchment paper and pie weights, and bake for another 5-10 minutes, or until the crust is lightly golden brown. Let the crust cool completely.

In a medium saucepan, combine the granulated sugar and water. Cook over medium heat, without stirring, until the sugar dissolves and turns into a deep amber caramel color.

Remove the saucepan from the heat and carefully pour in the heavy cream. Stir in the butter and salt until smooth and creamy.

Pour the caramel filling into the cooled tart crust. Let it set for at least 1 hour at room temperature, or until the caramel is firm.

Place the finely chopped milk chocolate in a heatproof bowl. In a small saucepan, heat the heavy cream until it just begins to simmer. Pour the hot cream over the chocolate and let it sit for 1 minute to soften the chocolate.

Gently stir the chocolate and cream together until smooth and glossy.

Pour the milk chocolate ganache over the set caramel filling. Spread it evenly to cover the entire surface.

Refrigerate the Milk Chocolate Caramel Tart for at least 2 hours, or until the ganache is firm.