Prepare the nuts: Coarsely chop 1 ½ cups of mixed nuts, finely chop the remaining ¾ cup.

Melt the chocolate: In a double boiler or heat-safe bowl, melt butter, semisweet chocolate chips, and dark chocolate chips. Stir occasionally until smooth. Remove from heat and cool for 10 minutes, stirring occasionally.

Add marshmallows and coarsely chopped nuts: Stir marshmallows and coarsely chopped nuts into the melted chocolate mixture until evenly coated.

Form the logs: Place two 15×18-inch parchment paper pieces on a flat surface. Spoon half of the chocolate mixture onto each piece, shaping each into a 12-inch log using parchment or a silicone spatula.

Chill the logs: Wrap the logs in parchment and chill for 15-20 minutes until firm on the outside but soft inside.

Prepare the pretzel coating: Mix finely chopped nuts and crushed pretzels in a small bowl. Place two more parchment paper pieces on the surface, sprinkling each with half of the pretzel mixture.

Coat the logs: Roll the chilled logs in the pretzel mixture, pressing gently to coat. Wrap tightly in parchment and chill for at least 4 hours or overnight.

Slice and store: Once firm, slice logs into ½-inch pieces. Trim any uneven ends.

Store: Layer cookies in an airtight container between waxed paper and store in the fridge for up to 3 weeks.