Melt the chocolate, butter, and sweetened condensed milk in the microwave in 30 second or one minute increments stirring until chocolate is melted.
Add salt and vanilla flavoring
Combine peanuts and marshmallows in a large bowl.
Pour chocolate mixture over nuts and marshmallows and stir until completely coated.
Spread on a large greased cookie sheet or 9x13 baking pan.
Refrigerate until set.
Cut into squares and store in air tight container, refrigerated or countertop storage.
Notes
Alternate TechniqueI always melt the chocolate in the microwave, but you have to be super careful as it doesn't look like it's melted and it is easy to go from melted to burned. For this recipe, I microwave it for about 2 minutes and then check it. If it is not melted, I microwave it 30 seconds at a time until it is almost melted.Then I take it out and stir it to finish the melting process because a microwave does not heat the ingredients the same throughout the dish, and some of it is very hot while the rest is not. When stirred, it melts the rest.