Combine the shallots, garlic, salt, and pepper in a small nonreactive saucepan over high heat. Stir in the stock and the wine and bring to a boil. Cook over high heat for 15 minutes. Swirl in the butter, remove from the heat, and continue to whisk in the butter until thoroughly incorporated. Serve immediately, or prepare without the butter and store, refrigerated, in an airtight container for up to 24 hours. Reheat in a small saucepan over low heat. When the sauce comes to a simmer, swirl in the butter and proceed from there.
Yield: 3/4 cup