Put a rectangular sheet nonstick baking paper (about 30x40cm) on a work surface and arrange the ham slices in a smaller rectangle the width of the fillet’s length (let the slices overlap slightly).
Lightly spread Dijon mustard on the ham, then put the fillet on top.
Carefully roll the fillet up in the ham, with the baking paper on the outside, and put it on a baking sheet.
Roast for 30 minutes.
Remove the fillet from the oven and leave the parcel to cool before removing the paper.
Meanwhile, make the salad dressing
Use a food processor or stick blender to blend all the dressing ingredients into a smooth, light green sauce. If it’s too thick, add a little water and mix until pourable, but still thick. Store in the fridge until you’re ready to serve.
To serve
Cut the meat into thin slices. Arrange with the salad ingredients on individual plates or on a serving platter, with the dressing on the side. Generously drizzle dressing over the salad.
