In a bowl whisk together the mustard, vinegar, sugar and parsley. Gradually add the olive oil, whisking all the time, until an emulsion is formed.
Add the chopped walnuts to the bowl and mix together. Season, to taste with salt and freshly ground black pepper.
To serve, place the rocket and chicory onto a plate, sprinkle with sesame seeds and spoon over some of the dressing, then place the crispy bacon on top.