I would go with the microwave melt of all the chocolates and add the nuts, probably some other nuts beside peanuts at my house. I have that recipe in a cook book.
I'd give them a zap of about 20 seconds and check what's going on in the bowl. If the mass is still stiff, I might go 30 more seconds and maybe a repeat or two. Microwaving chocolate depends on your microwave. I make a Summer Time fudge using Velveeta cheese, butter, choco chips and nuts and sometimes marshmallows for rocky road. If I remember right, I zap it in 20 or 30 seconds rounds until it a nice stirring consistency then stir in the nuts and if using them, the marshmallows. I wouldn't even fool around with a slow cooker for that Trisha recipe. into the micro wave at my house since I'm the boss here.