In a large pot, melt the butter and sauté the garlic and shallots for 3 to 5 minutes. Add the consommé and bring to a boil. Reduce heat to simmer. Strain off solids and return the mixture to the pot.
Add the wine and simmer for 15 minutes. Stir in the cornstarch mixture to thicken. Mix in the cream, tarragon, white pepper, and clam juice. Let stand for 30 minutes before serving.