Preheat the oven to 200°C (392°F). Line a baking sheet or two 8-inch tart tins with parchment paper.
Prepare the batter: In a large mixing bowl, whisk together the flour, water, olive oil, salt, and black pepper until smooth and lump-free. Set aside to rest while you prepare the topping.
Prepare the vegetables and wild garlic: Grate the potatoes and squeeze out excess moisture using a clean tea towel. Thinly slice the red onion, mince the garlic, and finely chop the wild garlic leaves. In a mixing bowl, toss the grated potato, red onion, garlic, and wild garlic with 1 tablespoon of olive oil and a generous pinch of salt.
Assemble the Scarpaccia: Evenly spread the vegetable and wild garlic mixture over the prepared tray or tart tins. Sprinkle over the thyme and rosemary. Pour the prepared batter evenly over the top, ensuring the vegetables are well coated. Drizzle with the remaining olive oil and season with additional salt and pepper to taste.
Bake the Scarpaccia: Bake in the preheated oven for 50–60 minutes, or until the edges are golden and crispy and the centre is set and firm. If the centre is still too soft, bake for an additional 5–10 minutes.
Cool and serve: Let the Scarpaccia cool for a few minutes before slicing into squares or wedges. Serve warm or at room temperature.