In a double boiler, while slowly stirring, melt the base chocolate (semi-sweet) over low heat - if you're doing 2 kinds of chocolate, do each separately
Once chocolate is melted, take off heat and mix in peanut butter
Pour mixture onto parchment lined baking sheet
If adding a second swirled white or dark chocolate, pour over and swirl in to a pattern with a knife
Sprinkle pretzels over top and put in the freezer to harden for 15 minutes
Once fully hardened, break up with a knife (in mild stabbing motions, don't go too crazy) or break it up by hand, and enjoy!