Scoop passionfruit pulp into a measuring jug (you’ll need 3/4 cup pulp). Squeeze juice from 1 orange. Stir pulp, 1/2 cup orange juice, sugar, ginger, mustard and rum in a small saucepan over low heat until sugar dissolves. Increase heat to medium and simmer for 10 minutes, stirring occasionally. Remove from heat and strain, pressing firmly with the back of a spoon, to extract 1 cup of liquid. Reserve seeds and discard ginger.
Preheat oven to 180°C. Line a large roasting pan with baking paper.
Remove rind from ham, except from the bone, by placing your thumb underneath to loosen. Reserve rind to store ham. Score fat in a diamond pattern with a sharp knife. Place ham in pan and brush well with a little passionfruit glaze. Bake for 20 minutes. Brush ham with more glaze and bake for a further 1 hour, glazing every 15 minutes, or until golden.
Halve remaining oranges and add to pan for the last 15 minutes of cooking. Add 1-2 tbs reserved seeds to remaining glaze and brush over ham. Serve ham garnished with thyme and oranges.
