Mix the cornstarch. Reserve about ½ cup (120 ml) of the measured milk. Whisk it with the cornstarch in a small bowl until smooth.
Warm the milk and sugar. Pour the remaining milk into a saucepan. Add the granulated sugar and vanilla sugar. Warm over low heat, stirring until the sugar dissolves.
Cook the cream. Stir the cornstarch mixture again, then slowly pour it into the warm milk while whisking constantly. Continue cooking gently, stirring along the bottom and sides, until the mixture bubbles gently and forms a thick, smooth cream.
Cool completely. Transfer the cream to a shallow bowl and press plastic wrap directly against its surface to prevent a skin from forming. Cool promptly to room temperature. Do not leave the cooked cream unrefrigerated for more than 2 hours.
Beat in the butter. Beat the cooled cream with an electric mixer until smooth. Gradually add the softened butter, mixing until evenly combined. The butter and cream should be at a similar temperature.
Add coconut and chill. Fold in the 250 g of desiccated coconut. Cover and refrigerate for 30 minutes, or until firm enough to shape.
Fill and shape. Divide the mixture into approximately 50 portions. Flatten each portion slightly in your palm, place one blanched almond in the center, and bring the filling around it. Seal and gently roll into a ball.
Coat the balls. Place the extra coconut in a shallow bowl. Roll each ball in coconut until coated, then place it in a mini paper cup.
Chill and serve. Arrange the finished balls in a container or on a covered tray. Refrigerate until firm and serve chilled.