Preheat the oven to 375°F (190°C).

Cut off the top of each of the heads of garlic, and brush each head with 1 teaspoon of extra-virgin olive oil and sprinkle with a pinch of salt. Wrap each bulb in parchment paper, then foil (to allow the garlic to steam and not burn, and to reduce aluminum transfer), and roast in the oven for 40 60 minutes, until tender. Allow the bulbs to cool, and then squeeze the garlic pulp out of the peels. This should yield 2 to 3 tablespoons of mashed roasted garlic. Set aside.

To make the dressing, throw the roasted garlic into the blender with the broth, lemon juice, mustard, salt, and pepper, and blast on high for about 30 seconds until smooth and creamy. Add the tarragon and process on medium for 5 to 10 seconds until broken up but not completely pulverized. Set aside.

In a large bowl, toss the romaine, apple, cucumber, celery and parsley. Stir in the dressing and serve immediately.