Preheat the oven to 200°C (fan).
Coat the potatoes with oil and salt, then place them on a rack in the center of the oven.
Blend three cloves of garlic with feta, lemon juice, seasoning, and enough garlic oil to create a thick, cream cheese consistency.
Melt butter, add chopped parsley and the remaining garlic.
Take out the potatoes and cut them into a six-star pattern (but not all the way through).
Fill the cuts with the cheese mixture.
Drizzle with garlic butter and parsley, and sprinkle some extra salt.
Return the potatoes to the oven for an additional 10 minutes to make them extra crispy.