Microwave the croissant for 10 seconds. Remove from microwave and, using a rolling pin, immediately flatten the croissant to ¼-inch thick (as thin as you can make it).
Heat ½ of the butter in a medium skillet over medium heat until melted. Place croissant in skillet, bottom side down, and press firmly with bottom of a smaller skillet or saucepan until lightly browned, about 3 minutes. Drizzle honey evenly over croissant and add remaining butter to skillet. Flip croissant over and press again, cooking until the top side is lightly browned and toasted, about 2 minutes. Remove to a plate to cool.
Spread Nutella over the croissant and top with berries as desired.
