Begin by making the ‘slaw. In a large bowl, combine the crème fraîche with the lemon zest and juice, mustard, capers and parsley. Stir through the shredded celeriac, then season well and set aside.
Cut the baguette lengthways in half and lightly butter one side. Top with the Parma ham, then spread with an even layer of the celeriac ‘slaw. Sandwich the halves and cut into 6 pieces.
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