To cook the caramelized onions: Heat a large Dutch oven or braiser over medium heat. Add the olive oil, followed by the sliced onions and salt. Stir to coat, then cook until the onions soften, about 15 minutes. Reduce the heat to medium-low/low and continue to cook, stirring occasionally, until the onions are a deep golden color, about 1 hour. Stir in the vinegar and cook for another 15 minutes—the onions should continue to deepen in color. Set aside until ready to use.
Caramelized onions also keep well in the refrigerator for a few days or in the freezer for a few months.
To toast the bread: When ready to cook the beans, heat a medium skillet with olive oil. Add the bread and toast until golden. Flip, repeat, then transfer to four plates.
To make the beans: Use the skillet you used to toast the bread. Add the nutritional yeast and cook over medium heat until fragrant, 1-2 minutes. Add the beans, enough of their broth to just cover, the caramelized onions, Worcestershire sauce, and the mushroom powder.
Bring the mixture to a low boil and cook, stirring often, until the sauce thickens into a gravy consistency. Taste and add salt if needed—I find that between the beans and the trio of flavors added, I don’t need to add salt.
Divide the beans on top of the toast and finish with black pepper before serving.
Video
Notes
Crust: When using whole grain bread or sourdough, I cut off the crust and save it for making breadcrumbs. I find the crust gets too hard and requires too much maneuvering.