Cut a slit down the back of prawns and remove the intestinal tract and discard.  Coarsely crush the pepper corns, fennel seeds and salt with a mortar and pestle.  In a glass or ceramic dish, stir together the crushed mixture, ⅓ cup of oil, lemon zest and juice to mix well.  Add the prawns and toss to coat well.  Cover with plastic wrap and place in the refrigerator for 1 to 2 hours to marinate.

Meanwhile, remove and discard the pith and flesh from the preserved lemon rind.  Finely dice the skin and stir through the mayonnaise to combine well. Set aside until needed.  Heat the remaining olive oil in a small saucepan over a medium heat.  Add almonds and cook for 1 to 2 minutes until golden, stirring occasionally.  Drain on paper towel.

Heat a large non-stick heavy based frypan over a high heat.  Remove half the prawns from the marinade draining off excess and cook 2 minutes each side or until just opaque. Add half the almonds and toss with the prawns for 30 seconds. Remove spice coated prawns and almonds and set aside.  Repeat with the remaining prawns and almonds.  

To serve, place four prawns on each plate with a pile of watercress, tossed with baby greens if using, alongside.  Accompany with the  preserved lemon mayonnaise.