For the Tuna, cut 8 fine strips from tuna, cover and set aside in fridge. Finely dice remaining tuna and place in a small bowl. Add soy sauce, mirin and grapeseed oil. Mix gently to combine, cover and refrigerate.
For the Pickled Salad, use a mandolin to thinly slice cucumber, kohlrabi and radishes. Place into a small bowl and add dill and vinegar. Place red radish, coriander and nasturtium leaves into ice bath.
Prepare Horseradish Cream by combining ingredients together in a small bowl and mix until well combined. Season to taste and set aside in fridge.
For the Avocado Mousse, place avocado flesh, lemon juice and miso paste into the bowl of a small food processor and process until smooth. Season to taste and set aside in fridge.
To serve, spread Avocado Mousse across serving plates. Place tuna slices at one end of mousse and marinated tuna at the other. Drain pickled vegetables then roll up cucumbers and kohlrabi slices and place onto plate. Add radish slices, drained leaves and Horseradish Cream. Garnish with edible flowers.