Heat the olive oil in a frypan with a lid over medium heat. Stir in the leeks and garlic, cook and stir 3 minutes until the leeks begin to soften. Pour in the white wine and bring to a simmer, then add the tomatoes, chicken stock, thyme and dill. Simmer, uncovered, until the liquid reduces to half.
Lay the fish fillets on top of the vegetables and cover the frypan. Cook until the fish is opaque and flakes easily with a fork, about 10 minutes. Ladle the sauce over the fish to serve.