Beat the butter and sugar using an electric mixer or wooden spoon until light andfluffy.
Add the condensed milk and vanilla extract and beat until smooth. Add the flour and salt, and beat until a smooth dough is formed.
Chill the dough for 30 minutes.
Roll out the dough thinly between two pieces of baking paper.
Chill the flattened dough again for 30 minutes.
Using a round cookie cutter, cut out circles. Place the chilled, raw cookies on a baking tray lined with baking paper. Bake for 12–15 minutes, or until golden brown. Cool on the baking tray for 2–3 minutes, then completely on a wire rack.
Prepare the royal icing according to package instructions. Ice the biscuits as desired, sprinkle over the crystallised edible flowers and allow to set.