Senegalese Onions - cooking recipe

Ingredients

6 onions (medium, white or yellow, not sweet or mild, sliced thickly - 1/3 inch slices)
4 garlic cloves (quartered)
1 cup vegetable oil (a mild oil, not olive oil)
1/2 cup whole grain mustard (not dijon)
1/4 cup brown mustard (basic, supermarket brand, not sharp)
1/4 cup lemon juice (embarrassed to say, I use jarred)
1/2 cup water
1 bay leaf
2 teaspoons bouillon (I use Better than Bouillon, chicken, but you could use the vegetable bouillon or two cubes)
1/2 teaspoon white pepper (I use white pepper because it adds a peppery depth, without any heat, but black pepper is better)
1/2 teaspoon salt

Preparation

Place all ingredients in a sauce pan.
Bring to a low boil.
Stir, making sure that onions on the bottom do not over-cook or stick.
Simmer for about 5 minutes. Check by tasting an onion; they should be noticeably softer but still a little al dente.
Turn off the heat and let the sauce sit at room temperature (I leave it all day, until dinner time).
Note: I leave the garlic & bay leaf in the sauce, as they continue to impart flavor, but the raw garlic can be jarring for some. Remove it or alert folks. After a couple of weeks, though, the garlic is deliciously pickled.
Serve room temperature as a relish alongside roasted meats. Or fry up in the roasting pan (using the pan dripping) and serve on top of meat, chicken, shrimp, etc.
Store the sauce/relish in the fridge; it last for several weeks.