The panna cotta can be made one day ahead.For the panna cotta:
To make panna cotta: Preheat oven to 300°. In a small saucepan, mix the cream and the gelatin. Set aside for 5 minutes. Heat the cream and gelatin with the sugar and the vanilla bean over medium-high heat. As soon as the mixture comes to a boil, remove the vanilla bean, add the egg whites (not beaten), and briefly mix with a whisk. Pour mixture into individual 1/2-cup molds and place molds in a high-sided baking pan. Pour hot water into pan so that it comes halfway up the side of molds. Transfer pan to oven and cook for about 25 minutes. Carefully remove from oven, take out the individual molds from the water bath and let them cool to room temperature. Put molds in the refrigerator to chill for another 3 hours.
To make strawberry skewers: In a medium-sized saucepan, boil champagne with 3 tablespoons of sugar until sugar dissolves. Put 24 strawberries in a large bowl and cover with the sweetened champagne. Just before serving, place 3 of the marinated strawberries on each of the 8 skewers. Turn panna cottas out onto serving plates and arrange 2 skewers on each plate.
To make sauce: In a blender, purée remaining 12 strawberries with 2 tablespoons sugar. Pour sauce over panna cotta. Serves 4