Put the spare ribs in a pressure cooker or a pan of water and add all other ingredients. Bring to the boil and cook under pressure for 15 minutes then let it depressurize by itself. Alternatively, bring to the boil in a pan, cover and gently simmer for an hour.
Let the ribs cool and transfer them to a plate. Chill them until you’re ready to bake them. Keep about 2 cups of the cooking water.
Mix the orange juice, maple syrup, mixed spice and half a cup of the cooking water in a small pan, then bring to the boil. Reduce it to a syrup, then let it cool.
Put the ribs in a baking dish and pour some of the cooking water over them, then brush them with the syrup.
Bake for 10 minutes, then turn them over, brush them again with the remaining syrup and bake for another 10 minutes.
Transfer the ribs to a platter and pour over the jus. Serve warm or at room temperature.