Mix together 1 tbsp each lemon juice
and white wine vinegar. In a measuring
jug, mix 100ml olive oil and 200ml
groundnut or vegetable oil.
In a food processor, whizz 2 egg yolks
with 1 heaped tsp Dijon mustard and
a generous pinch of salt until fully mixed.
With the processor still running, add a
few drops of the oil mix, incorporating
each drop before adding the next. Now
very slowly drizzle the oil in – the mayo
should begin to thicken and then stiffen.
If the mixture looks too thick, add 1 tsp
of your lemon/vinegar mix. Keep adding
the oil in the same way, alternating with
1 tsp at a time of the lemon/vinegar mix,
until all the oil is incorporated and the
mayo is the required consistency. Now
whizz in ½ small crushed garlic clove.
Whizz a 75g bag watercress, leaves
and stalks, with the mayo and season.
Add a little warm water, lemon juice or
vinegar to loosen, if needed. Chill and use
within 1 day – great with poached salmon.