Slice the fennel paper-thin, preferably with a mandoline. Slice the apple into thin strips and mix them immediately with the fennel and lemon juice so the apple doesn't discolour.
Add the mixed greens and olive oil and toss everything lightly. Grind some black pepper over it. The fresh, crisp salad provides a nice contrast to the fatty fish.
Spread the salad over a plate and place the smoked mackerel in chunks alongside it. Scatter with fresh dill sprigs. Mackerel provides valuable omega-3 fatty acids that support hormonal balance.