Place two pencils or chopsticks on either side of the potatoes and carefully slice the potatoes 1/2cm apart using a sharp knife.
Thinly slice the chilled butter and carefully wedge between each of the cuts in the potato. Drizzle olive oil, then add a pinch of garlic salt, rosemary and thyme to the top.
Place the potatoes onto a separate square sheet of aluminium foil and wrap tightly then, set them aside.
Set the Weber Q up for indirect cooking by placing a convection tray and trivet it onto the grill. Turn the gas control knob/s to the START/HIGH position and pre-heat the Weber Q for 10 minutes with the lid down.
Place potatoes onto the trivet and close the lid. Baby Q: Turn the gas control knob down to the medium setting and cook for 45 minutes to 1 hour until ready. Family Q: Turn the small gas control knob off and the large gas control knob to the Medium setting. Try to maintain a temperature between 200°C (390°F) to 220°C (430°F).
After 45 minutes, carefully unwrap a Hasselback potato and check if it has begun to fan out slightly and the texture is soft. Cook for a further 15-20 minutes if required.
Take the Hasselbacks out of the foil pack and add grated cheddar cheese between the slits, and sprinkle more on top as required. Then cook for a further 15-20 minutes on the medium-high setting uncovered until cheese has melted and golden brown.
Top with sour cream and leftover chives and serve with additional melted garlic chive butter.