Melt cocoa candy. Melt light cocoa candy according to package instructions. Place in 16 in. decorating bag. Cut ½ in. off tip of bag.
Pipe candy to fill pan. Tap pan lightly on surface to even out candy. Use spatula to smooth.
Immediately cover light cocoa candy layer with broken pretzels, pressing to secure.
Chill until set, about 30 minutes.