Landcress is really quite bitter. It needs to be countered with other strong flavors. Since it is so very easy to overcook, it's probably at its very best simply marinated. I like to marinade it for as long as possible.
For the marinade:
2 tbsp sunflower oil 2 tbsp soy sauce 2 tbsp spirit vinegar 1 tsp toasted sesame oil 1 tsp honey or maple syrup 1 tbsp wholegrain mustard 1 clove of raw garlic, pressed
(If raw garlic is too strong a flavor for you, roast some garlic until it's firm and grate it over the marinated landcress prior to serving)
Simply put all the ingredients into a cup and whip together until the oils have sufficiently blended with the other liquids.
Place 30g of landcress in a container and pour the marinade over the top. Marinade for at least one hour, shaking the container or turning it upside down occasionally.
When you’re ready to eat, take it to the table. This will serve two people.