Limes, clementines and citrus hybrids such as minneolas and tangelos all make delicious variations on the classic lemon curd, as do blood oranges, when in season. Here, we use pink grapefruit, which is one of our favourite citrus fruits of all, with its subtle sour-sweet bitterness and its vivid colour – so cheery on a dreary winter day. As with bitter marmalade, this curd probably appeals more to an adult palate, but we can’t get enough of its bitter edge, tempered – but only just – by a creamy sweetness. The ginger adds a mild buzz of heat, but is entirely optional. Spread it on toast, swirl through yoghurt or into home-made ice cream and sorbet, or use it to fill beignets or a cake for tea.