preheat oven to 350° with rack in the middle. spray 2-12 cup muffin tins
melt butter and unsweetened chocolate in pan and stir until smooth. pour into bowl with sugars, eggs and vanilla. sift flour and salt in and stir until combined.
stir in nuts, chocolate chips and snickers.
fill cups half way, bake until surface is glossy (20 mins).
top with marshmallows and cook until they start to melt (2mins).
cool enough to handle, remove from cups. cool.
combine caramel ingredients and microwave for 1 minute, stir until melted. drizzle on brownies. cool.
do not chill. keeps for 3 days in covered container.