Ensure the prawns are thawed if frozen.
Peel the prawns and devein them.
In a dry frying pan, gently toast the cumin, coriander, cloves and peppercorns over a medium heat for 1 to 2 minutes.
When toasted, pour them into a grinder and add the fenugreek, turmeric, paprika, chilli powder, cinnamon and salt, before grinding them into a fine powder.
Add the spice powder to a mixing bowl before stirring in the garlic, ginger and yoghurt. Mix thoroughly.
Coat each prawn in the marinade and place in the fridge for about 2 hours.
Heat up your BGE direct to about 400 deg F using the cast iron grill.
If not using a BGE, heat your grill as hot as you can.
Place the prawns on a skewer.
Grill on the BGE for about 2 to 3 minutes a side until the prawns are pink throughout and the marinade has caught in places.
If cooking under the grill, foil line the grill pan and place the prawns as close to the heat as possible for about 2-3 minutes a side.
Serve on lettuce with slices of lemon.