In a medium skillet, over medium high heat, heat the oil and saute the chicken, turning often, until well browned all over. Remove the chicken to a plate.
Saute the onion in the skillet until well browned.
Turn into the crockpot.
Place the tomatoes, orange, sugar, salt and pepper in the pot and set the chicken on top.
Rinse the skillet with the water and scrape into the cooker.
Add the bouillon cube.
Cover and cook on Low for 5 to 7 hours.
Before serving, remove the chicken to a deep serving dish and keep warm.
Turn the pot contents into a skillet, set the heat to high and simmer until thick enough to mound on a spoon.
Stir in the jelly and the sherry and cook, stirring until the sauce boils.
Do not overcook, lest the sauce lose its shiny quality.
If you wish, add some sugar or sweet sherry to further brighten the taste.
If sauce is not shiny enough, bring back to a very brisk boil and quickly stir in some jelly.
Pour sauce over the chicken.