Preheat oven to 375 F.
Place the potatoes, salt, stock, butter, garlic & thyme in a large casserole dish. Cover with a lid and simmer until potatoes are tender.
Remove the potatoes from the casserole and set aside, keeping them warm. Strain the liquid into large nonstick pan over medium heat and reduce until syrupy. Increase the heat to high and add the potatoes to the pan; continue to cook with the glaze. Add the baby leeks to reheat. Season with salt and freshly ground white pepper. Serve immediately.