Line two sheet pans with parchment or wax paper.
Melt white baking chips with coconut oil in a microwave-safe bowl for 30 seconds; stir. Heat in 15-second bursts, stirring until smooth.
Stir in vanilla extract until evenly combined.
Fold in chow mein noodles, peanuts, and shredded coconut until everything is well coated.
Scoop heaping tablespoons of the mixture onto the prepared pans to form small haystacks.
Sprinkle tops with sprinkles if using.
Chill pans for 15–20 minutes, or let stand at cool room temperature until set.