Confit duck leg with flageolet ragoût and celeriac mash

Ingredients

• 4 duck legs
• approx 15g table salt (you will need 15g/½oz salt per kilo of duck legs)
• 2-3 sprigs fresh thyme, leaves only
• 300g/11oz duck fat
• 1 banana shallot, finely sliced
• 1 garlic clove, finely diced
• 200g/7oz tinned tomatoes
• 400g/14oz tinned flageolet beans, drained and rinsed
• 200ml/7fl oz chicken stock
• 1 sprig rosemary, leaves finely chopped
• salt and freshly ground black pepper
• 50g/2oz butter
• 500g/1lb 2oz floury potatoes, peeled, cut into chunks
• 500g/1lb 2oz celeriac, peeled, cut into chunks
• 75g/3oz butter
• 110ml/4fl oz double cream