Put your potato slices between two paper towels and gently press to remove excess water.
In a large pan, add the butter, oil and thyme. Wait until the mixture is bubbling, then add potatoes. You may need to do this in batches (don’t pile them on top of one another, the potatoes should be lying flat in the pan). If you need to add more butter and oil, go ahead and add 1 tablespoon at a time.
Cook the potatoes until they are golden and looking almost crispy. Take them out of the pan, resting the slices on paper towels to get rid of excess oil.
Season with salt and pepper and sprinkle with scallions and parsley and top with sriracha mayo.