Mash the garlic and anchovy in a mortar and pestle with a pinch of salt and pepper. Transfer to a bowl and stir in the egg yolk followed by the buttermilk and cheese. Slowly whisk in the olive oil and finish with the lemon juice. Season to taste with salt and pepper. Cut the romaine leaves from the head and wash and dry them. Cut the outer leaves from the Belgian endive. Chill the greens well.
Chop the first third of the stem ends of both types of leaves into 1/4" strips across the leaves. Place them in a bowl with the remaining tips and drizzle the vinaigrette over. Toss well to coat the leaves evenly. Remove the core and slice the pear or apple into thin slices. Arrange them around the plates, alternating with the romaine and endive tips. Place the chopped greens in the center and sprinkle with the toasted walnuts