Preheat oven to 350 degrees. Butter a 9×13 inch baking pan. Set aside.
Melt butter in a small pan. Stir in vanilla Remove from heat and stir in pretzel crumbs until thoroughly combined. Press, using the back of a spoon or the bottom of a measuring cup into the bottom of the buttered pan taking care to reach all corners.
Evenly sprinkle the chocolate chips, then the peanut butter chips, peanuts, and finally the cornflakes over the pretzel layer. Pour the sweetened condensed milk evenly over the top, and spread with the back of a spoon or spatula until the mixture is evenly coated.
Bake for 25-30 minutes until edges are golden brown and the bars look “set”.
Allow to cool on a wire rack completely before slicing. This seems to take forever but resist the urge to cut them when they are even remotely still warm. You can refrigerate them before slicing if you are a clean lines fanatic. Store in the refrigerator or on a cool counter in an air-tight container.