Cook the couscous according to packet instructions. Season with salt and pepper, blend in the lemon zest, chopped spring onions, feta cheese, egg, asparagus and enough flour to bind. Mould the mixture into 4 cakes and shallow fry on each side until golden and set. Prepare a Hollandaise sauce by whisking the yolks over a pot of simmering water until creamy, add a spoon of hot water and whisk again, sauce should start thickening, repeat process twice more. Remove from heat, whisk in lemon juice and the melted butter. In a separate pan bring water to a simmering point, add vinegar, poach eggs in the cooking liquor. To serve, make a couscous cake onto a serving plate, spoon over 4 asparagus tips and top up with the smoked salmon. Lay an egg on top and spoon over the sauce, sprinkle with chopped dill.