Famous Jacket Potatoes

Steps

1. 1Preheat the oven to 220°C (conventional bake).
2. 2Pierce each potato 10–12 times all over with a fork to allow steam to escape during baking.
3. 3Rub the entire exterior of each potato with the 2 tbsp melted butter, coating every surface, then season lightly with ¼ tsp of the Kosher salt across all four potatoes.
4. 4Place the potatoes directly on the oven rack — not on a baking tray — on the center rack.
5. 5Melt 1 tbsp of the room-temperature butter in a skillet over medium heat.
6. 6Add the thinly sliced onion and cook, stirring for 30–35 minutes over medium-low heat, stirring every 4–5 minutes, until the onion is a deep, even mahogany-brown color and completely soft.
7. 7Season with a pinch of the remaining Kosher salt and set aside.
8. 8Bake the potatoes for 60–70 minutes total until completely tender when pierced at the thickest point with a paring knife.
9. 9Increase the oven temperature to 230°C. Allow the potatoes to cool for exactly 5 minutes — enough to handle, but not so long that the interior cools and becomes gluey.
10. 10Cut each potato in half lengthwise. Using a large spoon, scoop out the interior flesh into a large mixing bowl.
11. 11In the mixing bowl, add the remaining 3 tbsp room-temperature butter, 2 tbsp warmed milk, and the remaining ½ tsp Kosher salt to the scooped potato flesh.
12. 12Mash with a potato masher for 1 minute until very smooth, then fold in 100g of the grated cheddar and all of the caramelized onion until just combined — a few folds only, do not overwork.
13. 13Pile the filling back into the potato shells generously — mound it high above the rim of each shell. Scatter the remaining 50g grated cheddar over the tops of all four stuffed halves.
14. 14Return to the 230°C oven on the baking sheet and bake for 8–10 minutes until the cheese on top is fully melted, bubbling, and beginning to brown at the edges. Serve immediately while the cheese is still molten.
15. 15Top it off with chopped green onions to garnish, salt and pepper to taste.