Arrange charcoal briquettes into a pyramid and light according to instructions. After approx 15 minutes when the charcoals are white, it's ready to be spread evenly for cooking. Alternatively, preheat your oven to 200°C/400°F.
Thinly slice 1 lemon, and keep 1 lemon for squeezing. Slice garlic into slivers, and chop chives.
Cube butter in small cubes (to be placed inside the fish cavity or on top of fillet)
Prepare foil sheets, make sure they are larger than the fish. Best to use a thick foil when grilling, otherwise double the foil layers.
Squeeze lemon juice inside fish cavity, or over fillet. Lightly salt and pepper to taste.
Add the chives and garlic slices inside the trout cavity. Add several cubes of butter per fish.
Place a single fish in the centre of the foil. Place 2-3 slices of lemon on the skin side of the trout. Starting with the long ends of foil, fold foil loosely, crimping the edges together. Fold and wrap the short side of the foil until the fish is sealed, making a packet.
Place on the grill, or inside the oven on a baking sheet, for about 15 -20 minutes. The trout is ready when the flesh is opaque and it flakes easily with a fork.