Place all of the ingredients for the dressing in a mixing bowl. Use a fork to combine until the mixture turns a couple of shades darker and thickens. Pour in 3-5 tablespoons of water and mix until the dressing becomes the consistency of double cream. Taste and add more soy/vinegar or honey until it tastes perfectly balanced to you. Set aside.
If you are using the BBQ to cook the leeks, brush oil over both sides of the leek halves and sprinkle with salt. BBQ for 5-8 minutes on each side until the leeks are soft and dark char marks are visible all over. BBQ the lime, cut side down, for a couple of minutes. Remove the leeks and lime from the BBQ and drizzle the peanut dressing over the leeks while they’re still hot. Use tongs to squeeze the lime all over the leeks and serve straight away.
If you don’t have a BBQ, the leeks can be cooked on a griddle. Don’t oil the leeks, but place them on a griddle pan while they’re dry to cook for 8 minutes over a high heat on both sides. Remove from the heat and toss them in a bowl with enough oil to coat and a pinch of salt. Cooking them like this on the griddle pan prevents the leeks from sticking to the ridges and stops the oil smoking inside, which can turn it very bitter and acrid. Drizzle the peanut dressing over the leeks and serve straight away.