Cook and Prepare the Base: Cook the brown rice in a large pan of boiling salted water according to the packet instructions until tender, then drain thoroughly. While it cooks, lightly rub a large roasting tray (around 25cm x 30cm) with 1 teaspoon of groundnut oil. Spread the drained rice in an even layer in the tray—this will be the foundation that soaks up all the delicious juices.
Create the Magic Mango Glaze: Wash the mango. Carefully slice the two fleshy cheeks off the stone. Peel them and place the vibrant yellow flesh into a blender. Don't throw away the skin! Squeeze the remaining mango flesh around the stone over the blender to get every last drop of that sweet juice. Add the peeled garlic and ginger, finely grate in the zest of 2 limes, and squeeze in their juice. Add the soy sauce and 1 teaspoon of groundnut oil. Blitz on high for a minute until you have a beautifully smooth, fragrant purée. Pour this into a large bowl.
Make the Quick Pickle: Take the reserved mango skin and slice it very thinly. Halve the cucumber lengthways and use a spoon to scrape out the watery core. Finely slice the cucumber and the red chilli (leave the seeds in if you like heat!). Place the mango skin, cucumber, and chilli in a shallow bowl. Add the white wine vinegar and a good pinch of sea salt, then toss everything together. Set this aside to pickle while you cook the rest of the meal.
Assemble the Tray and Fire Up the Grill: Preheat your grill to a high setting. Using a sharp knife, carefully slice the skin off the salmon fillets. Reserve these skins. Pat the salmon fillets dry, then toss them in the bowl with the mango teriyaki glaze until they are fully coated. Place the glazed fillets directly onto the bed of rice.
Add the Vegetables: Trim the spring onions and chop them at a sharp angle into 2cm chunks. Cut the broccoli into small, bite-sized florets, and slice the stalk as well. Add all the vegetables to the bowl that had the mango glaze and toss them thoroughly so they're nicely coated. Scatter these glazed vegetables all around the salmon fillets in the tray. Now, lay the reserved salmon skins loosely on top of everything.
Grill to Perfection: Place the entire tray under the preheated grill for 12 to 15 minutes. You're looking for the salmon to be just cooked through and the edges of the vegetables and rice to be nicely charred.
Final Assembly and Serve: While the tray is under the grill, drain the excess liquid from your quick pickle. Pick the mint leaves and slice them finely. Toast the sesame seeds in a dry pan for a minute until golden and fragrant. Toss the mint and toasted sesame seeds through the drained pickle. To serve, place a portion of the rice, a salmon fillet, and some roasted veg on each plate. Add a crisp piece of salmon skin if you like. Top with a dollop of cool yoghurt, a generous spoonful of the quick pickle, and serve with wedges from the remaining lime.