If fish were frozen, thaw first and then pat dry with paper towels. Mix bread crumbs with seasonings. Bread fish with mixture, ensuring full coverage.
Melt garlic butter in heavy skillet on medium-high heat. Sauté mushrooms until just tender. Set aside.
Melt butter in heavy skillet on medium-high heat. Fry fish one or two at a time, few minutes each side, until they flake in centre. Set aside as they are done.
When all are done, place back into skillet with mushrooms and heat through before serving.
Serve with lemon slices.