Varieties
The European elder Sambucus nigra is edible (as is American Sambucus Canadensis), however mountain elder and dwarf elder are not.

Serving suggestions
Think of elderflowers as a flavouring - something like a fresh spice or herb. You could add them to a gooseberry compote or apple jelly, or steep them in hot cream to use for making custard. Elderflower cordial is very easy to make and can then be turned into sorbet. Traditional Italian recipes blend the flowers with ricotta and spices to make tart fillings and fritters. In Holland they are added to doughnut, cake and pancake batters. Whole flower heads can be dipped in batter and deep-fried to make a dessert. Savoury uses include mixing elderflowers with honey, wine, mustard and garlic to make glaze for roast lamb. In Alsace they are distilled in make an eaux de vie (water of life) spirit.

Preparation
Young elderflowers smell sweet and perfumed; they are past their best when sniffing them reminds you of the cat's litter tray! While it's important to use young flower heads, you should only use those that have fully bloomed. Pick them on a dry day (some say early in morning is best as it's thought that's when they're most fragrant) and use that same day. The stems are edible, though the stalks are normally removed unless using them as a handle, say in the case of dipping the flower heads into fritters. Recipes will distinguish whether you need whole heads or individual flowers.