In a large bowl, whisk together the flour, powdered sugar, and salt. Add the cold, cubed butter to the flour mixture. Using a pastry blender or your fingertips, cut the butter into the flour until the mixture resembles coarse crumbs.

Gradually add the ice water, one tablespoon at a time, mixing gently after each addition. Continue adding water until the dough just comes together. Be careful not to overmix; you want the dough to be slightly shaggy.

Form the dough into a disc, wrap it in plastic wrap, and refrigerate for at least 30 minutes. Chilling the dough prevents the butter from melting and helps develop a tender crust.

Preheat your oven to 375°F (190°C). On a lightly floured surface, roll out the chilled dough to about 1/8-inch thickness.

Use a cookie cutter or knife to cut out circles slightly larger than your tartlet tins. Gently press the dough circles into the tartlet tins, trimming any excess dough from the edges.

Prick the bottom of each tartlet crust with a fork. This prevents the crust from puffing up while baking. Bake for 15-20 minutes, or until the crusts are lightly golden brown. Let the crusts cool completely in the tins before removing them.

While the crusts are cooling, prepare the white chocolate ganache. Place the chopped white chocolate in a heatproof bowl.

In a small saucepan, heat the heavy cream over medium heat until it just begins to simmer. Do not boil.

Pour the hot cream over the white chocolate and let it sit for about a minute to allow the chocolate to melt. Then, gently whisk the mixture until smooth and glossy.

Once the tartlet crusts are completely cool, spoon the white chocolate ganache into each crust, filling them to the top.

Refrigerate the filled tartlets for at least 30 minutes, or until the ganache is set. This chilling time helps the ganache firm up and makes the tartlets easier to handle.

Just before serving, arrange fresh raspberries on top of the white chocolate ganache in each tartlet. Get creative with your arrangement to make them look extra appealing!