While the prawn marinates, whisk together the rice vinegar, soy sauce, canola and sesame oils, scallion and coriander seeds in a small bowl.
Heat the grill to high. Remove the prawn from the marinade, brush with canola oil, and season with salt and pepper. Skewer the prawn and grill for 2 to 3 minutes per side, until just cooked through.
Toss the spinach with some of the vinaigrette and mound in the center of a serving platter. Arrange prawn around spinach and spoon over more of the dressing. Scatter the peanuts over the salad and prawn.
For the New-Style Scampi:
Add the butter and red pepper flakes to the marinade in the food processor, and pulse until combined. Scrape the mixture into a small saucepan and put on the grill just to melt the butter.
Trim the ends from the limes and halve. Brush with canola oil, season with salt and pepper, and grill, flesh side down, until marked and slightly softened, 4 to 5 minutes.
Skewer the remaining prawn, brush with canola oil, and season with salt and pepper. Grill for 2 to 3 minutes per side, until just cooked through. Slide the prawn from the skewers into a shallow bowl, pour over some butter sauce, and toss to coat. Scatter the coriander seeds over the top, and arrange the grilled limes around the prawn.