3 smashed potato thyme gratin Recipes

butter (2 oz), brown onion, sliced thinly (150g or just under 5 oz), leek, white and inner green tender leaves, thinly sliced, garlic cloves, crushed, roast potatoes, cut into halves (just over 19 oz), plain flour, milk (250ml/8 fl.oz. ), fresh thyme, finely chopped, sea salt, to taste (add with caution as the potatoes were undoubtedly salted when first cooked), fresh ground black pepper , to taste, sunflower seeds (optional), rindless bacon, fat removed, chopped, cheddar cheese, coarsely grated (120g or just under 4 oz)

unsalted butter, softened , for the baking dish, celery root (about 1 lb), extra-virgin olive oil, red bliss potatoes, bartlett pear, sea salt and freshly ground pepper, heavy cream, garlic , smashed, grated gruyere cheese (about 3 oz), grated parmesan cheese (about 2 oz), chopped fresh thyme