In an electrical blender mix the biscuits and 120gr of the mini pretzels to crumbles.
Melt the margarine in a casserole. Mix with the crumbles.
Cover a baking form with a paper and press the crumbles evenly on the bottom and a bit up on the edges.
Place in the fridge for 2-3 hours.
Heat the heavy cream on low heat in a casserole. Add 300gr of the chocolate and let it melt. Continue stirring for a few minutes.
Take away the chocolate ganache from the heat and let it cool for 15 minutes. Pour it slowly in on the cake bottom.
Place the cake cold for 1 hour.
Melt the rest of the chocolate and cover the rest of the mini pretzels with chocolate. Place the chocolate covered mini pretzels on a paper and let the chocolate get hard.
Place some of the mini pretzels on the cake and serve.