Celeriac, sage and black garlic gratin

Method

1. Heat the oven to 160°C fan/gas 4. Put the milk, cream, garlic and sage stalks in a saucepan, bring to the boil, then remove from the heat. Finely slice the celeriac into 3-4mm thick pieces (use a mandoline if you have one).
2. If using a black garlic bulb, peel the cloves and mash with the back of a spoon, adding a splash of water to create a paste. Put the sage leaves in a blender or food processor with the breadcrumbs and whizz until you have
   a fine green crumb (you can also just finely chop the leaves and mix with the breadcrumbs).
3. Layer up the celeriac slices in the oven dish, spreading each layer with a little of the garlic paste. Discard the sage stalks from the cream mixture, then pour it over the celeriac. Sprinkle the cheese on top, followed by the breadcrumbs, then bake for 1 hour. Cover with foil if the top starts to darken too quickly.