Taught me how to fry an egg. Maddeningly coy (it assumes you've the proficency of a master chef too), it leaves out some crucial recipes, like his crayfish gratin--in the opinion of some, his masterpiece.
And as for least favorite, check this out, from Rosie Tinne's Irish Countryhouse Cooking:
1/2 lb spaghetti—cooked and cold
1-2 lb white fish—cooked and cold
1-2 pt white sauce—cold
1 (or more) tin shrimps
1 dessertspoon curry powder
1 teaspoon lemon juice
1 teaspoon redcurrent jelly or apricot jam
Mix all ingredients gently together, sprinkle with parsley or paprika. Chill and serve.