Line the bottom of the Varoma with baking paper by wetting it under a cold tap, scrunching it up and then spreading it over the bottom of the Varoma (no need to use the Varoma tray, middle insert, for this recipe).
Add one litre of water to the Thermomix bowl, place the potatoes in the lined Varoma together with the half lemon and cover with the lid (no need to use the tray): 30 minutes, Varoma, speed 2 and a half. Check that they are done and place them in a large salad bowl. Squeeze the lemon over them and discard it, also make sure any of the lovely citric juices left in the parchment paper are tipped into the salad bowl with the spuds.
Dry Thermomix bowl, add chilli and coriander: 4 seconds, speed 5. Add the 50 g feta: 2 seconds, speed 5 (keep going if you would like it all chopped quite small). You could, of course, make this mix as step one and reserve (I just didn’t want an extra bowl to wash).
Many thanks to The 4 Blades for the addition of this step: add the potatoes, lemon juices, extra virgin olive oil to the bowl: 5 seconds, reverse, speed 4 (being careful not to turn it to mush!). My previous option was to just drizzle the potatoes with a bit of extra virgin olive oil and add the chopped coriander, chilli and feta directly from the TM bowl and mix well. Either option is very easy as you can see. Ready in a jiffy.