First, put some potatoes on to boil in salted water. They will take about 20 minutes to cook. Meanwhile, poach a couple
of skinless smoked cod fillets in 150ml milk for about 6 - 7 minutes, until just cooked. Remove and keep warm, while you
finish off the sauce. Add a couple of Tbs crème fraîche to the poaching milk and simmer for a few minutes, until the sauce
reduces and thickens a little, then season with salt and freshly-ground black pepper, whisking in a few small chunks of
diced cold butter to enrich the sauce. Return the fish to the sauce, scatter with chopped chives and simmer for another
minute or so. When the potatoes are cooked, drain and return to the pan and add a good knob of butter. Mash to a smooth
consistency, adding a good handful of grated strong cheddar cheese. Dollop some cheesy mashed potato onto a warm plate,
top with the fish and spoon the sauce over the top.