Step 1. Make the Pastry
- In a large mixing bowl, rub the cold butter into the plain flour and salt until the mixture resembles breadcrumbs.
- Gradually add cold water, 1 tablespoon at a time, mixing until the dough comes together.
- Wrap the dough in cling film and chill in the fridge for 20-30 minutes.
Step 2. Prepare the Filling
- Boil the diced potatoes in salted water until tender, about 10-12 minutes. Drain and set aside.
- In a skillet, melt the butter and sauté the sliced onions over medium heat until soft and golden, about 8-10 minutes.
- Add the cooked potatoes, double cream, thyme, and half of the grated cheese to the skillet. Mix gently and season with salt and black pepper. Remove from heat and let cool slightly.
Step 3. Preheat the Oven
Preheat your oven to 200°C (400°F).
Step 4. Roll Out the Pastry
- On a floured surface, roll out the chilled pastry dough to fit your 8-inch pie dish.
- Line the dish with the pastry, trimming any excess. Prick the base with a fork to prevent puffing.
Step 5. Assemble the Pie
- Spoon the potato and onion filling into the pastry case, spreading it evenly.
- Top with the breadcrumbs and the remaining grated cheese for a crunchy, cheesy topping.
Step 6. Bake the Pie
Bake in the preheated oven for 25-30 minutes, or until the pastry is golden and the topping is bubbling.
Step 7. Cool and Serve
Allow the pie to cool slightly before slicing. Serve warm with a fresh green salad or steamed vegetables.