Measure all the ingredients before doing anything else. Once the chocolate begins to melt it all goes rather fast.
Line a pan with parchment paper.
Chop the pecans and pistacchios.
Chop the chocolate and put in a double boiler or over a water-bath.
Add the butter...
..as well as the sweet condensed milk.
Stir and remove lumps.
Stir the batter.
Add the mini marshmallows...
..and the chopped nuts.
Just blend, don't over do it or you risk that the marshmallows melt. Pour the batter into the cake pan. Put in the fridge to make easier to cut later.
Cut in chunks..