Stir the tofu and curd into a smooth cream.
In a small saucepan, gently heat the water with the agar-agar powder until dissolved and the water boils. Pour the liquid into the curd cream and mix thoroughly so that the agar is evenly distributed.
Stir in the cucumbers, spring onions and tarragon, season with salt and pepper.
Beat the egg whites until stiff. First only 1 tablespoon of it, then carefully fold the remaining snow into the tofu cream.
Pour into a large enough bowl and chill for 3-4 hours before serving.