In a food processor, crush pretzels into fine crumbs.
In a medium bowl, mix pretzel crumbs, sugar, and margarine. Place a 9-inch nonstick tart pan with a removable bottom on a sturdy cookie sheet so it’s easier to remove from the oven. Press mixture onto the bottom and up the sides of the pan using a small juice glass to press the mixture down and make the crust even.
Bake for 10 minutes. Remove from oven and let cool completely on a wire rack, about 20 minutes.
Reduce oven to 325 F.
Combine chocolate chips, sugar, and salt, in a medium bowl. In a small saucepan, bring soy milk to a simmer; do not allow to boil. Pour soy milk over chocolate chips and stir until chocolate is melted and smooth, about 2 minutes.
Gently whisk eggs, one at a time, into chocolate mixture. Pour into tart shell and bake for 15 to 20 minutes until filling is set and the surface is glossy. If you see any bubbles or cracks forming on the surface, take the tart out immediately or the filling will be overcooked. Let cool on wire rack for 10 minutes.
Cover with plastic wrap and refrigerate until ready to serve.
Just before serving, top with 1/4 cup roughly chopped pretzels. Serve with nondairy whipped cream.