Preheat the oven to 200°C/fan 180°C/gas mark 4. Place the cauliflower florets in a food processor and blitz in two batches until fine. Place in a large microwave-proof bowl, cover with cling film and cook for 8 minutes on a high heat, stirring halfway through until just cooked.
Leave the cauliflower to cool, then place in a clean tea towel and wring out until very dry. Place in a bowl and mix with the eggs, 50g cheese and the spring onions. Line a wide baking sheet with greaseproof paper. Divide the mixture into 8 and shape into 11 x 9 cm rectangles on the greaseproof paper. Bake for 18-20 minutes, until golden brown and just set.
Preheat the grill to high and top half the cauliflower toasts with the remaining cheese. Place under the grill for 2 minutes, until melted, then top the cheese with the sliced gherkins. Top this with the other half of the cauliflower toast and place back under the grill until golden brown. Serve with the salad leaves on the side.