Preheat the oven to 110ºc.
Lay out as many baking sheets as you possess and line them with a silicone mat or baking parchment.
Whisk the egg whites to soft peaks.
Add the cream of tartar and salt.
Add the sugar slowly while continuing to whisk at high speed. It should look glossy and stiff.
Using a tall jug to hold your piping bag, scoop about half of the mixture into the bag. Cut the tip off the end, not too big.
If you want to make toadstools, put a quarter of the remaining meringue mixture into another bowl and mix with the food colouring.
Save the rest of the meringue mixture for sticking the stems and caps together and adding little white spots to the toadstools. Keep in an airtight container.
Pipe your mushrooms stems. Holding the piping bag directly over the baking sheet, with the tip close to the sheet, pip a cone shape (1.5cm x 2 or 3 cm height). You need about 20.
With a wet finger, slightly flatten the top of each one - you need it flat so that it fits onto the cap of the mushrooms. Some of the stems will fall over, so pipe extra. You want them straight and upright.
Pipe the cups. Pipe circular mounds about 5cm across and 2 cm high. Pipe about 20. Smooth the top of each one with a wet finger. Finely grate the liquorice on top of the caps.
For toadstools, using another piping bag, pipe the same size and number of caps (about 20), using the red meringue.
Bake the caps and stems for 45 minutes, making sure they don't go brown.
For the toadstools: make a teeny hot at the end of another piping bag, spoon in some of the leftover white meringue and pipe little white spots on top of the red caps. Then bake them for another 15 minutes.
Remove from the oven and leave to cool completely.
Melt the chocolate either in a bain-marie or in a microwave in 30 second bursts. using a pastry brush, paint the underside of the white mushroom caps with the melted chocolate. Then stick the stems on to the undersides of the caps and leave to dry. Handle with care.
For toadstools: use the leftover meringue mixture to stick the stems to the red dotted caps, cap side down, then place them back on a baking sheet and bake for 5 minutes until dry. Leave to cool.
Optional: instead of liquorice dust, dust, using a tea strainer, cocoa powder over the tops of the white mushrooms to give that speckled mushroom look.