Ok, so I tried this and it mostly worked. My crock doesn't get hot enough on low, and the lid kept in too much moisture. The stewed onions still tasted awesome, but they were runny and didn't have the concentrated flavor of the stovetop.
Next time I'm going to try this with my crock on high the lid partially off for part of the cooking time.
Julia Winter wrote:OK, so the recipe is:
-fill crockpot with sliced onions and fat
-run on high (with the lid on) until onions are translucent
-switch to low and take off the lid, run it overnight on low
Am I right? I figure you could vary the fat depending on what you have and what you like.