Sooner or later it happens to us all. The business meeting stretches way beyond schedule. A child must be taken to the doctor. The friend arrives unexpectedly from out of town. Suddenly there's little time to shop for supper and even less to cook. Anyway, who wants to make elaborate preparations in the heat?

On such occasions I've found these recipes invaluable, not least because they adapt to whatever ingredients you can find. The Provenc,ale soup calls for the widest possible range of vegetables, with the choice up to you. One of those packages of mixed stew vegetables sold by enterprising markets would be handy here. Pasta adds body to the soup, and chopped parsley a touch of freshness.

Anyone who has encountered the Provenc,ale garlic mayonnaise called a parsley. Serve crou tes and garlic mayonnaise separately. Crou tes can be spread with mayonnaise and soaked in soup, or eaten out of hand. GARLIC MAYONNAISE (Makes 1 cup)

If egg yolks are cold, or if oil is added too fast, mayonnaise may separate. If it does, start again by adding curdled mixture to another egg yolk.

8 to 10 cloves garlic, peeled

2 egg yolks

Salt and pepper to taste

1 cup olive oil

Juice of 1 lemon, more if needed

In a food processor or blender, pure'e garlic and egg yolks with salt and pepper. With blades turning, add a tablespoon of oil, drop by drop, until mayonnaise starts to thicken. Remaining oil can be added more quickly, in a slow, steady stream.

Work lemon juice into mayonnaise and taste for seasoning. Mayonnaise can be made up to a day ahead and kept, tightly covered, in refrigerator. Let it come to room temperature before serving; do not stir when it is cold or it may separate.

Quick Garlic Mayonnaise: Beat 8 to 10 crushed garlic cloves into 1 cup prepared mayonnaise and season to taste with lemon juice. MELON WITH STRAWBERRIES AND PORT (4 servings)

Liqueur or sweet white wine can be substituted for the port.

2 small ripe melons

1 quart strawberries

2 tablespoons sugar, more if needed

1 cup port wine

Sprigs of mint for decoration Halve melons and discard seeds. With a ball cutter, scoop out flesh in balls. Scrape shells clean, cut a slice from base so they sit firmly, and chill them.

Hull strawberries, washing only if they are sandy. Halve them if large and add to melon balls with sugar and port. Taste, adding more sugar if necessary, and chill.

Just before serving, spoon mixture into melon shells and garnish.