First make the dressing by placing all the ingredients in a screw-top jar and shaking until well combined. As the Roquefort is quite salty, there is no need to add any salt.
Cut the celery into 5 cm lengths, then slice again lengthwise into thin strips.
Core and thinly slice the pears lengthwise and place in a large bowl with the Belgian endive leaves, salad greens, nuts and celery. Add the dressing and toss well to coat evenly. Crumble the Roquefort over the salad.
Place a slice of the toasted pumpernickel or walnut bread on each plate and pile the salad evenly over the top. Serve immediately.
Variations: Other blue cheeses would also work well. For a lower-fat alternative, try feta cheese. For a more tropical flavour, you could replace the pears with 2 sliced mangoes. For a lighter-flavoured dressing, replace half the walnut oil with a light olive or sunflower oil.
Each serving: 11.5 g protein, 22 g fat of which 6 g saturates, 40 g carbohydrate, 9.5 g fibre, 419 Calories