This recipe makes about 1 1/4 cup, enough for 4 people. For 70 pieces of chicken, it needs about 10 times this recipe. Is it anywhere near close to yours?
You would double the recipe and make it 5 times, storing in preheated thermoses.
(Makes 1 1/4 cups)
1 tablespoon minced shallot
1/2 cup dry Champagne
2 tablespoons Champagne vinegar
1/2 cup heavy (whipping) cream
4 tablespoons unsalted butter, cut into small pieces
Salt and freshly ground white pepper to taste
Place the shallot, Champagne, and vinegar in a small saucepan over medium heat. Bring to a boil and cook to reduce by one third. Add the cream to the pan, and cook to reduce again by one third.
Remove the pan from heat but keep the burner on low. Whisk in the butter one piece at a time. Return the pot to the burner for a few seconds if the sauce cools too much to melt the butter. Season the sauce with salt and pepper, adding a minimum of salt since the prosciutto is salty. Strain the sauce through a fine-meshed sieve and keep it warm over hot water.
Note: The sauce may be made up to 2 hours in advance and poured into a warm thermos.