To make the crêpes, combine all the ingredients in a bowl to make a batter. Set aside for half an hour to settle.
To cook the crêpes, heat 1 tablespoon of olive oil in a frying pan and add a ladleful of the batter. Cook for 1 to 2 minutes on each side, then remove from the pan. Repeat with the remaining batter.
Combine the ricotta, crème fraîche, lemon zest and juice in a bowl and season with salt and pepper. Stir until smooth, then add the chopped smoked salmon and diced avocado.
Spread a layer of the smoked salmon mixture onto each crêpe and add some rocket leaves. Roll tightly and refrigerate until required.
Cut in half on the diagonal and serve with some extra rocket and a lemon wedge if desired.