350g/12oz peeled celeriac (about ½ large one), finely sliced
1 garlic clove, finely chopped
3 tbsp finely chopped flatleaf parsley
300²µ/10½´Ç³ú potato (1 large baking potato), peeled or scrubbed and cut into 1cm/½in slices
2 banana shallots, finely sliced
1½ tbsp capers, rinsed well and drained
1½ tbsp Dijon or grainy mustard
sea salt and freshly ground black pepper
300ml/10fl oz full-fat crème fraîche
500ml/18fl oz full-fat milk
50–100g/1¾–3½oz air-cured ham, such as Parma or Serrano, thickly sliced (optional)