Preheat oven to 350 degrees & spray a 9x13 glass baking pan with cooking spray. Set aside.
Mix cake mix, evaporated milk & melted butter in mixer beating well.
Add 1 cup Snickers bites & beat well to break them up a bit.
Transfer 3/4 of batter to prepared pan & spread out flat in bottom as best you can. It's very sticky.
Bake 10 minutes - pull out.
Top with Snickers Bites
Drop remaining batter on top- do not spread out.
Return to oven & bake another 40-45 minutes
Check with toothpick test- should be mostly clean.
Remove & allow to cool completely before cutting.
Store at room temperature in airtight container.