Melt butter in a medium saucepan over medium heat and stir in flour. Cook for 1 minute

Pour in the milk in two batches, stirring well between each addition. Continue to stir until there are no lumps, about 5 minutes. Remove from heat and stir in salt and cheese. Set aside

Preheat oven to 220°C/200°C (fan-forced). Line a baking tray with baking paper

Working inside the pastry square, score a smaller square approx. 1-1 ½ cm from the edge. Prick middle of pastry several times with a fork. Bake 10 minutes. Pastry should have browned and puffed up

Push down cooked pastry centre and spoon over cheesy sauce leaving the pastry border free. Dollop over pesto and arrange mushrooms over the top, leaving room for the eggs to nest in

Crack an egg into each space and season with salt and pepper. Bake 10-12 minutes or until eggs white are cooked and yolks still runny

Stand for 5 minutes. Cut into 4 large squares, serve warm