Reduce the heat to medium and melt the butter in the same skillet. Add the crushed pink peppercorns and shallot; sauté until softened, about 1–2 minutes.
2 tablespoon butter, 1 tablespoon pink peppercorns, 1 shallot
Add in the garlic and thyme leaves, let sizzle for about a minute, until the garlic is very fragrant. Then turn off the heat.
2 teaspoon garlic, 2 teaspoon fresh thyme leaves
Add the whiskey to deglaze the pan, scraping up any browned bits. Let it simmer for 30 seconds to 1 minute to cook off most of the alcohol. Then turn the heat back on.
¼ cup whiskey
Stir in the beef stock (and any juices in the sous vide bag), Dijon mustard, and balsamic vinegar. Simmer for 3–4 minutes, reducing slightly.
½ cup beef stock, ½ teaspoon Dijon mustard, 2 teaspoon balsamic vinegar
Add the heavy cream and continue to simmer until the sauce thickens enough to coat the back of a spoon, about 2–3 minutes.
¼ cup heavy cream
Whisk in 1 tablespoon cold butter to finish the sauce. Season the peppercorn sauce with salt to taste.
1 tablespoon cold butter, Kosher salt