In a small bowl, mix together the sage, salt, pepper and garlic.
Rub over tenderloin.
Place ½ cup water in a crock pot along with the tenderloin.
Cook on low for 6 - 8 hours.
1 hour before the roast is finished, mix together the ingredients for the glaze.
In a small sauce pan brown sugar, cornstarch, balsamic vinegar, water and soy sauce.
Heat over medium heat and stir until mixture thickens; about 4 minutes.
Brush roast with glaze 2 or 3 times during the last hour of cooking.
For a more caramelized crust, remove from crock pot and place on aluminum lined sheet pan, glaze; set under broiler for 1 - 2 minutes until bubbly and caramelized.
Repeat 2 to 3 more times until desired crust is achieved.
Serve with remaining glaze on the side.
