Heat butter over medium-low heat for 2 minutes until melted. Remove from heat. Add flour, cornstarch, baking powder, 50 g sugar, 5 packs vanilla sugar, desiccated coconut, and sweet cream. Mix until combined into a dough and knead for 1 minute. Cool the dough for 10 minutes.
Divide the dough into marble-sized pieces and shape each into a small croissant. Place on a greased baking sheet. Bake at 180 °C (356 °F) on the middle rack for 20 minutes.
While the croissants bake, mix 50 g sugar and 4 packs vanilla sugar in a bowl.
Remove the hot croissants from the oven and toss each one in the vanilla-sugar mixture to coat. Set aside to cool for 15 to 20 minutes. The croissants may feel soft straight from the oven but will firm up as they cool.