Refrigerate mini peanut butter cups for at least an hour. Remove from the refrigerator and with a sharp knife, slice peanut butter minis in half. Return to the refrigerator until needed.
Line 8-inch-square baking pan with foil. Lightly butter.
Combine sugar, evaporated milk, butter and salt in medium, heavy-duty saucepan. Bring to a full rolling boil over medium heat, stirring constantly. Boil, stirring constantly, for 4 to 5 minutes. Remove from heat.
Vigorously stir in 12 oz bag marshmallows, chocolate chips and vanilla extract. Stir vigorously for 1 minute or until marshmallows are melted. Quickly stir in chopped minis and mini chocolate chips.
Pour into prepared baking pan; refrigerate for 2 hours or until firm. Lift from pan; remove foil. Cut into 48 pieces.