Heat the milk and 200ml water in a small pan over a gentle heat until steaming but not hot. Whisk together the yeast, 2 tsp sugar, the oatmeal, flours and salt in a bowl. Pour in the warmed milk and stir until the mixture resembles a thick batter. Cover and leave to prove in a warm spot for 1-2 hrs until increased in size and bubbly.

Heat a dry, non-stick frying pan over a medium heat and fry the mushrooms for 8 mins until browned, stirring occasionally. Stir in the thyme and garlic, and fry for 2 mins until fragrant. Season and set aside.

Brush a little of the oil over a non-stick frying pan set over a medium heat. Pour in a ladleful of batter and swirl the pan to coat the base. Fry for 2-3 mins until set and browned on the bottom, then flip and repeat. Take care when flipping, as they can break quite easily. Repeat with the remaining batter.

To serve, return the pan to the medium heat, carefully lay in an oatcake and spoon some of the mushrooms over half of it. Sprinkle over a little of the grated gruyère. Fold the oatcake in half to create a semi-circle and enclose the filling, and fry gently for 1-2 mins until the cheese has melted. Repeat with the remaining oatcakes, mushrooms and cheese. Serve straightaway.