Put the chicken, wild rice, carrot, celery and broth into the slow cooker and grind plenty of black pepper over the top.
Set it to low and leave it alone for six hours, by which time the wild rice will have split open and gone tender.
Lift the chicken out onto a board and shred it into rough pieces, then tip the whole lot straight back into the pot.
Whisk the arrowroot into the evaporated milk until smooth, pour it in, and stir until the broth turns thick and glossy.
Give it fifteen minutes more on low to come together, then taste it and add a last grind of pepper before you serve.
