Preheat the oven to 190°C/170°C fan/gas 5. Dry-fry the bacon for 5 minutes in a skillet until crisp, then cut into tiny pieces. Boil the entire potatoes for 5 minutes, then drain and set in a dish of cold water.
STEP 2
When the potatoes are cool enough to handle, blot them dry and coarsely shred them into a large mixing basin. To keep them from sticking, toss them with oil as you go. Grate the onion coarsely and wring off any extra liquid before stirring it into the potatoes with the bacon.
STEP 3
Warm up a baking sheet in the oven for 5 minutes. Butter a 23cm loose-bottomed cake pan generously. Scatter the potato over the pan, careful not to pack it down, then dot with butter all over the surface. Place the potatoes on a heated baking sheet and bake for 1 hour and 20 minutes, or until they are cooked through and crisp on top.
