In a dry heavy skillet cook the sugar over moderate heat until it begins to melt and continue cooking it, stirring with a fork, until it is melted completely and is golden caramel. Remove the skillet from the heat, stir in the pumpkin seeds and the sesame seeds, and, working quickly, pour the mixture onto a sheet of foil. Let the brittle cool and break into small pieces. **The brittle may be made 1 week in advance and kept in an airtight container.**