Heat a large pan over medium high heat, when the pan is hot, add a drizzle of olive oil.

Add the sliced mushrooms with the butter and cook until mushrooms have softened and released their juices.

Remove from heat and stir in the garlic and thyme, the residual heat in the pan will cook the garlic.

Finally, season to taste with salt and pepper. Leave to cool for 10-15 minutes.

Pre-heat the oven to 200°C / 180°C fan assisted.

Roll out the rectangle of shortcrust pastry onto a baking tray lined with parchment paper.

Mix through half of the grated Dubliner Mature Red and White cheese with the mushroom mixture then evenly spread this on top of the shortcrust, leaving a 5-6cm border around the edges. Sprinkle the remaining grated cheese over the top.

Fold the edges over the filling then brush the dough border with beaten egg. Finally, sprinkle the dough border with flaky sea salt.

Bake in the pre-heated oven until crust is golden, 35-40 minutes. Leave to cool for about 5 minutes before serving.