To make the crust combine the pretzel crumbs, soft butter and
powdered sugar. Using finger tips, rub together until combined and the
mixture forms large, coarse crumbs. Place in a tart or pie pan and with
the back of a small glass, firmly press the crumbs evenly in the bottom
and up the sides of the pan. Bake for about 10 minutes in a 350 degree
oven until the edge of the crust just begins to brown. Remove from the
oven and set aside while preparing the filling.
To make the filling, coarsely chop the chocolate and place in a
medium bowl with the butter. In a small pan bring the cream just to a
boil and pour over the chocolate and butter. Let sit for about 5 minutes
and gently stir with a spatula until the chocolate has completely melted
and the mixture is smooth. Do not use a mixer or a whisk to minimise
creating bubbles or beating excess air into the mixture.
Pour into the cooled crust and refrigerate overnight. To serve,
slice into small wedges.