For key visual process photos, refer to the body of the blog post.
Make the crepes:
In a high-powered blender, combine the egg, melted butter, whole milk, all-purpose flour, granulated sugar, salt, vanilla extract and goldenberry powder (if using).
Blend on high-speed until incorporated, about 30 seconds.
Pour the mixture through a sieve into to a mixing bowl or large measuring cup to remove any lumps, and lightly cover with plastic wrap.
Place into the fridge to rest for 1 hour.
Cook the crepes:
Heat up a large frying pan over low heat.
Add a little butter and swirl it around.
Pour about ¼ C of crepe batter to the pan (using a 9" diameter frying pan -- if using a different size, you may need to adjust accordingly) and swirl around evenly.
Cook for 1-2 minutes on one side (do not flip).
Use a spatula to carefully remove the crepe and transfer to a wire cooling rack to cool completely.
Repeat with the remaining batter.
Make the whipped cream:
In a bowl, combine the heavy cream, powdered sugar and vanilla extract.
Whisk until the cream stiffens and holds a firm peak (but be careful not to overwhip).
Assemble the crepes:
Place a crepe (smooth-side down) on a clean work surface.
Add a dollop of whipped cream to the center.
Place a chunk of mango on top of the cream.
Add another dollop of whipped cream over the mango.
Working from the bottom, gently fold up the crepe to cover the whipped cream and mango.
Fold in both sides.
And fold over to enclose, seam-side down.
Place the mango pancake onto a plate.
Repeat with the remainder.
Store in the fridge until ready to serve.
Notes
Crepe batter yields approximately 8 x 9" round crepes.