Preheat and Prepare: Preheat your oven to 220°C (200°C fan). Place a large, sturdy baking tray in the oven to heat up. This will help the potatoes start crisping immediately.

Boil the Potatoes: Place the potatoes in a large pot and cover with cold water. Add the tablespoon of sea salt. Bring to a boil and cook for 15-20 minutes, or until they are completely tender and a knife inserts with no resistance.

Drain and Steam-Dry: Drain the potatoes thoroughly in a colander. Return the empty pot to the low heat for a minute to evaporate any remaining water, then turn off the heat. Tip the potatoes back into the dry pot, cover with a tea towel (not the lid), and let them sit and steam-dry for at least 5 minutes. Give them a gentle shake halfway through.

Prepare the Garlic Butter: While the potatoes are drying, melt the butter in a small saucepan over a low heat. Add the minced garlic and fresh thyme leaves and cook gently for 1-2 minutes until fragrant. Be careful not to let the garlic burn. Remove from the heat.

Smash the Potatoes: Carefully remove the hot baking tray from the oven. Drizzle with the 2 tbsp of olive oil. Arrange the steam-dried potatoes on the tray, leaving plenty of space between them. Use the base of a glass or a potato masher to firmly press down on each potato until it’s about 1.5 cm (just over 1/2 inch) thick. Don't press so hard they disintegrate! I find that a firm, steady press works best.

First Roast: Drizzle the smashed potatoes generously with the prepared garlic thyme butter. Season with the cracked black pepper. Roast for 20-25 minutes, until the edges are golden brown and starting to look crispy.

Add the Cheese: Remove the tray from the oven. In a small bowl, mix the grated Cheddar and Parmesan together. Sprinkle the cheese mixture evenly over the top of each potato.

Final Roast: Return the tray to the oven and roast for another 10-15 minutes, or until the cheese is completely melted, bubbling, and golden brown in spots.

Serve Immediately: Let the potatoes cool on the tray for a minute or two, which helps them firm up slightly. Garnish with fresh chives or parsley and serve hot.