2 Tbsps.unsalted butter 6 Tbsps.bacon fat 3 cups onion, finely diced 1 /2 cup shallot, finely diced 2 Tbsps.garlic, minced 1 ½ tsps.dried thyme 3 ½ tsps.salt, divided 2 medium carrots, peeled and thinly sliced 3 cups small new potatoes, sliced 1 /3 -in. thick 4 small ripe tomatoes, peeled, seeded and chopped 1 cup dry white wine 8 cups water 5 lbs.catfish fillets,cut into 1 ½ -in.pieces 1 tsp.ground black pepper 3 Tbsps.chopped parsley 1 /2 cup thinly sliced green scallions (white and 2-in.green)
In a heavy saucepan, heat the butter and bacon fat until foaming. Add diced onion and shallots; cook and stir for 5 minutes. Toss garlic, thyme and 11⁄2 tsps. salt into the pan, and cook 5 minutes longer.
Add carrots and potatoes; cook and stir for 5 minutes. Add chopped tomatoes, white wine and water; bring to a simmer. Continue simmering, skimming the surface occasionally, until the potatoes and carrots are tender, about 15 minutes.
While soup is simmering, season catfish pieces liberally with remaining 1 tsp. salt and black pepper.
When potatoes are tender, add seasoned catfish, parsley and scallions to the saucepan. Simmer, partially covered, for 5 minutes. Taste for seasoning, adding additional salt and black pepper as desired.