Lightly spray a 9-inch round pan with cooking spray.

Melt butter in a large saucepan over medium-low heat until golden brown and nutty, then remove from heat.

Add marshmallows and stir until almost completely melted. Stir in vanilla, salt, and green food coloring until smooth. Mix in the crispy rice cereal until evenly coated.

Press the mixture evenly into the prepared pan. Let it cool for 20 minutes.

Cut the set treats into 8 equal wedges. Gently press a pretzel stick into the bottom of each wedge to serve as the trunk.

Melt white chocolate chips in a microwave-safe bowl in 20-second increments, stirring until smooth. Transfer to a piping bag, snip the corner, and drizzle over each tree. Decorate with sprinkles immediately.