Slow Cooker Black Bean Tacos with Mango and Avocado

olive oil

small yellow onion, finely chopped

red bell pepper, seeded and finely chopped

celery stalk with leaves, finely chopped

garlic cloves, minced

jalapeno, seeded and minced

minced fresh ginger root

bay leaf

ground cumin

ground allspice

dried oregano

– 15.5 oz. cans black beans, drained and rinsed

water

brown sugar

kosher salt

freshly ground black pepper

whole wheat flour tortillas

ripe mangoes, peeled and diced

ripe avocado, thinly sliced

Chopped cilantro, for serving (optional)