For the Walnut Vinaigrette: To make vinaigrette, put the walnuts, shallots and mustard in a mixing bowl. Add the vinegars and whisk to combine. Slowly drizzle in the oils in a stream while whisking to emulsify the vinaigrette; season with salt and pepper. Keep any remaining vinaigrette covered in the refrigerator for up to five days.
For the Salad:
Bring a large pot of salted water to a boil over high heat.
Blanch green beans for 30 seconds; they become tender very quickly. Using a slotted spoon, remove beans from water and plunge into an ice bath to “shock” them, i.e., to stop the cooking process and cool them down right away. This procedure also sets their vibrant green color. Drain green beans in a colander and put in a mixing bowl. Bring the water back to a boil. Add beets. Cover the pot, reduce heat to low and simmer for 20 to 25 minutes. To check for doneness of the beets, insert a paring knife into the centers – it should slide in without any resistance. Transfer beets to an ice bath.
Once they are completely cool, rub off the skins off with paper towels. If using red beets, wear rubber gloves and put down a piece of wax paper on your cutting board – otherwise everything will turn red! Cut beets in half or in quarters, depending on their size. Add beets to green beans. Add the heirloom tomatoes. Dress with 1/2 cup of walnut vinaigrette, tossing with tongs to coat the salad evenly. Season to taste with salt and pepper. Divide salad equally among chilled plates. Top with blue cheese.
Makes 1 cup vinaigrette | Serves 4 entrée, serves 8 starter