Drain cherries, reserving syrup.
Combine cherry syrup, sugar and cinnamon stick in saucepan, bring slowly to boil, simmer gently 3 minutes, strain.
Blend arrowroot with a little water, stir into cherry syrup mixture, return to heat, stir until sauce boils and thickens.
Add pitted cherries, heat thoroughly.
Add warmed brandy, ignite.