I have no recipe, just some ideas which may or may not work. Strictly an experiment.

First, I would add 1/2 cup of chocolate flavor malted milk powder to a white or caramel-flavor cake mix. This would be baked in a 9" x 13" pan, cutting the baked cake in half crosswise. The two pieces will be stacked upon each other, trimming them if necessary to mimic the proportions of a Milky Way candy bar.

Then I would melt some Kraft caramels together with a little heavy cream (which would make a softer caramel) and spread that between the layers and on the top of the top layer. I can only guess how many caramels this might take... Maybe two bags?

I would frost the entire cake with a pourable milk chocolate ganache (which will set up in the refrigerator to a more or less solid state) and try to simulate the wavy pattern that a real candy bar has.

I have a recipe that makes a bundt-type cake which calls for melting MW candy bars and adding them to the batter. I assume that isn't the cake you're asking for, is it?