Melt butter, peanut butter, and marshmallows in a large nonstick pan over medium - low heat
Stir the marshmallow mixture frequently until almost fully melted and combined - it will continue to melt when removed from heat
Remove from heat and immediately add in protein powder and cereal
Stir with a silicone spatula until combined well
Transfer to a mixing bowl. Using a large cookie scoop, create even portions or bites and place on a parchment paper lined baking sheetYou could also make bars by transferring the cereal mixture directly to a square pan lined with parchment paper or sprayed with nonstick spray - although they will be pretty thin!
Optional - heat chocolate chips and coconut oil in a microwave-safe bowl until fully melted (I only do ~10-15 seconds at a time so it doesn't burn)
Drizzle chocolate topping evenly over rice krispies treats
Allow to cool completely and transfer to an airtight container. Store at room temperature.If in a square baking pan, use a sharp knife to slice into even portions before transferring to an airtight container
Consider wrapping the individual cereal bars in plastic wrap and storing in the fridge or freezer to enjoy at a later date
Notes
Nutrition facts will vary depending on specific items and amounts used.