Halve, stone and scoop out the avocado flesh, then mash with the crème fraîche until completely smooth. If you’re worried about it discolouring, add a small squeeze of lemon juice. Season with a little sea salt and ground black pepper, if you like.
Finely slice the radishes, then pick and finely chop the dill. Toss the radish slices with the dill, vinegar and a little pinch of salt.
Spread the avocado over the crispbread or rye toast slices, then top with slices of salmon.
Sprinkle over the radish slices, then finish with a scattering of the cress and leaves, and a drizzle of rapeseed oil. Serve with lemon wedges.