Place the celery, carrot and brown onion into a food processor and process on high to finely chop the vegetables. If you don’t have a food processor you can finely chop all the vegetables by hand.
In the slow cooker: Drizzle the olive oil over the base of a slow cooker. Add the vegetables, duck breast and then top with canned tomatoes. Add in the oregano and season with salt and pepper. Cook on high for 4hrs. Use two forks to shred the duck into the sauce.
OR on the stove: Heat the oil in a large heavy base pot on medium heat. Add the vegetables and fry off for 3mins. Then add in the duck breast, canned tomatoes, oregano and season with salt and pepper. Bring to the boil and then reduce to low heat and cover, cooking for 1hrs. Stir occasionally to prevent sticking. Use two forks to shred the duck into the sauce.
Heat the zucchini noodles in a fry pan for 1 min then top with ragu to serve.