On a lightly floured cutting board, roll out 1 piece of puff pastry into a rectangle about 1/16-inch thick. Brush generously with the melted butter, then place in the refrigerator for 10 minutes to set the butter. Repeat with the remaining sheet of puff pastry.
Lightly brush the top of the puff pastry with ice water. Arrange the candy bars in a line on the bottom edge, leaving a small space between each. Using a pizza wheel, cut the pastry into strips between the candy bars. Roll the candy bars up tightly, pressing the edges to seal. Place in the freezer to rest while oven heats up.
Preheat the oven to 400 degrees F. Line 2 baking sheets with parchment and arrange the croissants at least 4 inches apart, seam-side down. Brush well with melted butter, then bake for 15 minutes. Brush again with butter, rotate the pans, and bake until golden brown, about 10 minutes more. Allow to cool for at least 20 minutes before serving.