Melt caramels with half the evaporated milk in a double boiler or in microwave (about 1 minute in microwave at a time, then stir in between & repeat until melted).
Meanwhile, mix together:
cake mix (do not follow directions on box),
half the evaporated milk,
butter or margarine.
Spread half the cake mixture evenly over the bottom of a 9x13 pan (may need to use fingers to press down & smooth).
Bake @ 350 degrees for 8 minutes.
Layer on top of baked mixture: nuts, white chips, peanut butter chips, and half of the chocolate chips.
Pour the melted caramel mix evenly over all.
Sprinkle the rest of the chocolate chips over the caramel. Carefully spoon the rest of the cake mixture over the top (in small clumps). Sprinkle the M&Ms over all (use different colored ones for special holidays, sports parties, etc.)
Bake 15 - 18 minutes. Cool partially, then score. It's less mushy if it rests overnight but great on ice cream when it's fresh out of the oven.