Combine the Rice Krispie cereal and mini marshmallows in a large mixing bowl, then set the bowl nearby. Keep the marshmallows evenly distributed so every cluster gets both crisp cereal and chewy bites.

Melt the white chocolate or vanilla almond bark in a microwave-safe bowl using gentle 30-second bursts, stirring between each burst, then stir in the creamy peanut butter. Stop heating when the mixture looks glossy and completely smooth, with no thick or grainy patches around the sides.

Let the warm peanut butter coating stand briefly, then pour it over the cereal and marshmallows and fold gently with a spatula. The mixture should feel warm rather than hot against the inside of your wrist, and the marshmallows should remain puffy.

Scoop mounds onto the lined baking sheet with two spoons, topping each one with mini chocolate chips if using. Leave a little space between clusters so their rough, craggy edges can hold their shape as they firm.

Leave the cookies at room temperature for 2 hours, or until the coating is fully set, then transfer them to an airtight container. A firm cluster releases cleanly from the parchment without leaving a tacky coating behind.