1. lightly brown butter over low heat. Pour into a large enough bowl. Cool until firm once again. Slit vanilla bean lengthwise, scrape out pith. Remove the peel from the ginger, grate, weigh out 30 g.
Mix powdered sugar, butter, vanilla pulp and salt until creamy. Fold in 2/3 flour by spoonfuls and ginger. Knead in the rest of the flour.
Form dough into 4 rolls (approx. 3 cm ø), then into squares. Coat with beaten egg white and turn in brown sugar to the other side. Leave to cool for 3-4 hours.
Cut rolls into slices about 1/2 cm thick. Place on baking sheets lined with parchment paper with enough space between them. Bake in a heated kitchen oven (electric oven: 225 °C /fan: 200 °C /gas: level 4) for 6-7 minutes. Cool.