Miscellaneous with tomatoes

1/2 pound mushrooms small 1 1/2 cups fish stock 1/2 cup greek olives pitted (black) * 4 each halibut steaks cut into 3/4inch slices * 1 x milk * 1 x salt * 1[...]

4 medium tomatoes ripe 14 tablespoons butter unsalted, cut into, pieces, plus more as, needed 4 small onion white, thinly, sliced 2 tablespoons shallot finely[...]