In a large frying pan, quickly toast the almond flakes until golden. Tip them into a bowl and set aside for later. Wipe the pan clean with a kitchen towel and use it again for the asparagus.
Trim off the woody ends of the asparagus and, for the thicker woodier spears, peel the lower third. Cut the spears diagonally into 3 cm pieces and fry over medium heat with a bit of oil and 1/2 tsp salt for around 6-8 minutes.
In the meantime, pick the tarragon leaves and roughly chop them. Peel the garlic clove and grate it into a glass, then add the extra virgin olive oil, vinegar, mustard and 1/3 tsp salt. Mix well to combine (or use a jar and shake it). Pop the sourdough slices into the toaster.
Pour the lentils into a large mixing bowl followed by the asparagus, the dressing and most of the chopped tarragon and flaked almonds. Toss well to coat evenly and serve in two plates with the remaining tarragon, almonds and the toasted sourdough slices.