Historic Walloon pickled fish: fresh river trout or whitefish pan-fried in flour, steeped in an aromatic vinegar marinade with sweet onions, thyme, cloves, and lemon jelly.
Season the fish pieces with salt and pepper, dust in flour, and fry in hot oil for 3 to 4 minutes until golden and crisp. Drain on paper towels.
In a saucepan, bring the vinegar, white wine, sliced onions, bay leaves, thyme sprigs, cloves, and peppercorns to a boil. Simmer for 8 minutes until onions soften.
In a stoneware terrine, layer the fried fish, lemon slices, and cooked onions.
Pour the hot spiced vinegar over the fish. Let cool, cover, and chill in the fridge for at least 24 hours so the natural fish gelatin sets the marinade into a light jelly. Serve cold with rye bread.