For the cucumber salad and the dressing, mix together all the ingredients for the cucumber salad together. In a separate bowl, mix the ingredients for the dressing, adding just enough lime juice and oil to slacken the jam, and to your taste. Chill the salad and dressing.
For the grilled tomato chutney, preheat the grill. Lay the whole tomatoes and garlic on a baking tray and drizzle with a little olive oil. Grill until well charred. Peel the garlic, then place on a large chopping board with the tomatoes and the rest of the chutney ingredients. Chop together finely to combine. (Or pulse in a food processor to a chutney consistency.) Keep chilled until required.
For the John Dory, marinate the fish in the lime juice with a pinch of salt for 20 minutes.
For the batter, mix the garlic and ginger pastes and all the dry ingredients in a bowl, then slowly pour in the sparkling water, whisking as you do so. Wipe the fish with kitchen paper to remove excess moisture, then add the fish to the batter. Leave for ten minutes.
Meanwhile, make the crushed peas. Lightly blanch the peas in boiling salted water for one minute, then drain. Heat the butter and oil in a frying pan. Add the asafoetida and, as it foams, add the cumin seeds. When the cumin seeds crackle, add the chilli flakes and the blanched peas. Cook for 3-4 minutes, then stir in the stock (or water) and cream, and season with salt and freshly ground black pepper. Remove from heat and, with a wooden spoon, crush the peas. Keep warm while you fry the fish.
To fry the fish, heat the groundnut oil in a deep heavy-bottomed saucepan, until a breadcrumb sizzles and browns when dropped in it. (CAUTION: hot oil can be dangerous - do not leave unattended.) Deep-fry the fillets for 3-5 minutes or until golden and crisp on both sides. Carefully remove with a slotted spoon and drain on kitchen paper. Sprinkle with the chaat masala.
To serve, toss the cucumber salad with dressing to taste. Spoon the crushed peas onto each of four large warm plates. Place the fish on top, then pile some of the cucumber salad on the fish. Spoon a little tomato chutney around each plate.