In a mixing bowl, combine all-purpose flour, cocoa powder, sugar, and salt. Cut in cold butter until the mixture resembles coarse crumbs. Gradually add cold water until the dough holds together. Shape into a disk, wrap in plastic, and refrigerate for 30 minutes.

Preheat your oven to 350°F (175°C). Roll out the chilled dough to fit a tart pan, pressing it into the fluted edges. Trim excess dough, line with parchment paper, and add pie weights. Bake for 15 minutes, then remove weights and parchment, baking for another 5-7 minutes until set. Allow to cool.

In a saucepan, heat heavy cream over medium heat until it simmers. Pour over chopped dark chocolate in a bowl and let sit for a minute. Stir until smooth, then stir in vanilla.

Pour the ganache into the cooled crust, smoothing the top. Cover with plastic wrap and chill in the refrigerator for at least 2 hours.

After the ganache has set, arrange sliced fresh strawberries on top. Optionally dust with powdered sugar.