Sweet, delectable lamb's liver is a favorite dish in Ireland—to do this dish justice, use the liver of a young spring lamb.
2 lobes (about 1 lb.) fresh, young lamb's liver,
2 cups milk
8 tbsp. butter
1 large yellow onion, peeled and finely chopped
1 tbsp. Irish whiskey, preferably Jameson or Powers
1⁄2 cup heavy cream
1 tbsp. whole-grain mustard
Freshly ground black pepper
1 tbsp. chopped fresh garlic chives
1. Slice liver crosswise into 1/4"-thick slices and put in a single layer into a shallow dish. Pour milk over liver, sprinkle with 1/2 tbsp. salt, cover with plastic wrap, and refrigerate overnight.
2. Transfer liver to a colander, gently rinse, and drain. Lay liver slices in a single layer on a sheet tray and pat both sides dry. Melt half the butter in a large skillet over medium heat. Add onions and cook, stirring often, until soft and just beginning to brown, 12–14 minutes; transfer to a bowl. Working in 3 batches, melt remaining butter and quickly sear liver until slightly golden on both sides, about 1 1/2 minutes per batch, transferring liver to a plate when done.
3. Stand back and carefully deglaze skillet with whiskey (it may flame). Add cream and mustard, whisking to remove any bits from bottom of pan. Cook until sauce has thickened slightly, about 1 minute. Return onions and liver to pan with any juices that have accumulated. Season to taste with salt and pepper and cook until liver is just heated through, 1–2 minutes. Garnish with garlic chives and serve with crusty white bread, if you like.