Cut a thin slice from the top of the loaf. Scoop out most of the bread. Tear to make 1.5 cups soft crumbs (top slice and remaining bread can be used as bread crumbs in other recipes). Brown onion and mushrooms in 1.5 tbs. of the butter. Beat egg with catsup. Mix in bread crumbs, half cup of the cheese, wine and seasonings. Lightly mix in ground beef and onion mixture. Spoon meat mixture into hollowed-out bread. Rub crust with remaining half tbs. butter. Wrap in foil. Bake at 190ºC or 1 hour to 1.25 hours. Fold back foil and sprinkle with remaining half cup cheese. Return loaf to oven. Bake until cheese melts, about 3 minutes. Cut into 3 cm slices.