Combine verjus, vinegar, shallots, and pepper in a small bowl.
Line 2 or 3 platters with crushed ice. Nestle oysters on top, keeping them level. Garnish with lemon wedges if you like and serve with mignonette.
* Verjus is juice pressed from unripe grapes, and its mild acidity--versus the higher acidity of vinegar--makes it easy to pair with wine. Find at well-stocked grocery stores and sweetwatercellars.com.