In an electric mixer fitted with the paddle attachment, combine the butter, half of the pretzels, and the sugar; beat until creamy. Beat in the flour and egg. Add in the remaining pretzels. Turn the dough out onto a piece of plastic wrap. Wrap up and refrigerate for at least an hour.
Roll out the dough (using extra flour, as needed) to at least 12 inches across. Press the dough into the bottom and up the sides of a square or round, fluted tart pan (10 inches). Freeze for at least 20 minutes, until firm.
Preheat oven to 350 degrees.
Line the tart shell with parchment paper and fill with pie weights. Bake for 30 minutes, until nearly set. Remove the paper and weights and bake for 15 minutes longer, until firm and golden.
Allow to cool and then brush the shell with the melted chocolate. Refrigerate until set.
In a medium saucepan, bring the cream to a simmer.
Turn off the heat and add in the milk chocolate with almonds. Allow to star for 5 minutes, and then whisk until smooth. Allow the filling to cool to room temperature.
Pour the filling into the shell. Refrigerate until set (at least 4hours). Sprinkle with salt, crushed pretzels, and serve with caramel and crème fraîche.