Grate or blitz in the food processor 2 medium/large carrots and celery.
Add the veg and minced beef to the slow cooker and sprinkle the flour on top. Using a wooden spoon or spatula mix the flour into the mince and veg completely.
Tip the 500 mls of passata, 3 tbsp of ketchup and salt and pepper on top and stir through.
Push in the rosemary sprig and put the lid on. Cook on low for 4 hours. It will be ok for 6 but not for any longer as it may start to burn on the bottom of the pot.
Scoop out the rosemary when you are ready to go. I try not to stir it to keep the rosemary all in one place so I can remove it easily.
Video
Notes
Season well, this dish benefits from quite a bit of salt.
If you prefer it sweeter then add another 2 tbsps of ketchup or a tsp of sugar.
A point to mention is that you can make this in a large frying pan or saucepan too. It doesn't have to be made just in a slow cooker. Let the bolognese bubble in the pan on a low heat for 45 minutes. Stir occasionally.
I try not to stir too much as it will cause the leaves to come off the rosemary sprigs and my children don't like to munch on them. I scoop them out before serving.
Don't omit the flour as it thickens the spaghetti sauce.
Use the best mince you can afford. It does make a difference.
Reheat the leftovers in the microwave covered until piping hot for super easy midweek meals.