1. Toast sesame seeds in a heavy pan over medium heat until they are a shade darker. Set aside to cool. 2. Simmer sugar and 1 cup of water in a large heavy saucepan, stirring, until sugar is dissolved. 3. Gently stir in figs, zest, rum and lemon juice and simmer, uncovered, stirring occasionally, until thick and syrupy. Depending on the size of your pan and heat level this could take just under an hour or twice that long. 4. As the jam becomes, well, jam-like, check the consistency. If it seems too thick and chunky for your taste, stir in a little of the remaining water. 5. When it looks properly jammy, remove from the heat and gently stir in the sesame seeds. 6. The jam will keep, covered in the fridge, for a month or two - if you can keep your hands off it that long.