1. Mix the pesto, white truffle balsamic glace, and olive oil together in a small bowl. Place chicken breasts in a glass bowl or other glass container and pour the marinade on top. Make sure the entire surface of the chicken breasts is covered with the marinade, and then refrigerate the chicken for a few hours or overnight.
2. When you are ready to make the pizzas, fire up your grill. When it is very hot, grill the chicken breasts for approximately 5 minutes per side, until cooked through (grilled time will depend on the thickness of the chicken breasts; thinly sliced breasts will take less time and thicker ones will take more time).
3. Set aside the chicken breasts until you're ready to top the pizzas. Place the pizza stone on the grill to preheat.