Darina Allen: Whip these recipes up for National Mousse Day

Rory O'Connell's Leek Mousse with Mussels an Sauce Bretonne
Today, to coincide with National Mousse Day (who dreamed that up?), we’ll have a celebration of a few of my 1970s favourites – time-honoured classics that have stood the test of time, and are still high on the list of special requests on the Ballymaloe House menu.
How about a leek mousse? Leeks are at their best just now, I’ve been digging the smaller ones from the vegetable garden, I can’t bear to waste a scrap.