Watercress, leek and celery

In whatever shop or supermarket I go, the suggestions for Eastern jump at me. All very uninspiring. Eggs: boring. Lamb: boring. This will not do. Maybe the first asparagus will be for sale later this month. That would be nice. In the meantime I dive into the Badische Kueche and see what the traditional dishes for this month are:
Kressesalat, Brunnenkressesuppe, Bodenseehecht nach Herzog Gunzo, Kalbshirn: Gardencress, Watercresssoup, Pike from the Bodensee and Calfsbrain.
We also get some gardenlore from Ottenhofen: One must plant peas on Good Friday, then the worms will keep away, onions and garlic on saint Benedictsday and potatos in april when the moon is full.

The watercresssoup sounds nice.
You need: 40 g. leek, but only the white part, 20 g. celery, 200 g. watercress, 40 g. (soy)butter, 40 g. riceflour, 1 l. stock, 100 ml. dry white wine, 200 g. sweet (soy)cream, 2 eggyolks.
And this is what you do: wash and dice the leek and celery, wash the watercress and separate the leafs from the stalks.
Put the butter in a saucepan and let it melt a little, stir in the leek and celery and let them get yellowishgold but not brown. Stir in the flour carefully and then the stock. Bring it to boil but keep on stirring. Let is softly boil for ten to fiftieen minutes.
Chop the watercressleafs. Pour the soup through a strainer and bring it back to boilingpoint. Add the white wine. Mix the cream and the eggyolks in a bowl and stir it into the soup and keep stirring while it thickens. Just before serving, add the watercress.