In a baine-marie, heat up the egg whites, sugar, and salt until 160F, continuously whisking. Transfer to a mixer bowl and whisk for several minutes, until thick and glossy.
Transfer to a piping bag with a round tip and place in the fridge for several minutes to cool. Pipe a circle of meringue and use a spatula to flatten it out a bit. Place in the freezer to harden.
Melt milk chocolate in the microwave, let cool a little bit. Dip the biscuits with the meringue side down in the chocolate. Return to the freezer for the coating to set, eat straight from the freezer.
Note: For a wagon wheels version, spread some raspberry jam on the biscuits before layering the meringue.