Step 1: Make the Shortcrust Pastry

• In a mixing bowl, rub the butter into the flour and salt until the mixture resembles breadcrumbs.
• Gradually add cold water, 1 tablespoon at a time, until the dough comes together.
• Roll the dough into a ball, wrap it in cling film, and chill in the fridge for 20-30 minutes.

Step 2: Prepare the Onions

• In a frying pan, melt the butter over medium heat.
• Add the sliced onions and cook slowly for 15-20 minutes, stirring occasionally, until soft and caramelized. Season with salt and pepper and set aside to cool slightly.

Step 3: Roll Out the Pastry

• Preheat your oven to 200°C (180°C fan).
• Roll out half of the chilled pastry on a floured surface until it’s about 3mm thick. Use it to line the base of a 20-23cm pie dish, trimming off any excess.
• Prick the base with a fork and chill for 10 minutes.
• Blind bake the pastry by lining it with baking paper and filling it with baking beans. Bake for 10-12 minutes, then remove the paper and beans and bake for another 5 minutes until the base is golden. Set aside to cool.

Step 4: Make the Filling

• In a mixing bowl, whisk together the eggs and double cream until well combined.
• Stir in the grated cheddar cheese and caramelized onions, seasoning with salt and pepper.

Step 5: Assemble the Pie

• Pour the cheese and onion filling into the prepared pastry case.
• Roll out the remaining pastry to make the top crust. Dampen the edges of the pastry base and place the top crust over the filling. Trim and crimp the edges to seal.
• Brush the top of the pie with egg yolk for a golden glaze.

Step 6: Bake the Cheese and Onion Pie

• Place the pie in the preheated oven and bake for 25-30 minutes, or until the pastry is golden brown and the filling is bubbling.
• Remove from the oven and allow the pie to cool for 10 minutes before serving.

Step 7: Serve the Pie

• Slice and serve warm, alongside a fresh green salad or steamed vegetables for a complete meal.