Pre heat oven to 180 c ff / 355 f.
Grease a 16cm x 21cm (6.5" x 8") baking dish if using (or a bit larger - see notes) and set aside.
Take the same pan you fried the crumb mixture in, add 2 tsp of olive oil and put back over medium low heat.
Add onion, carrot & bacon to pan and fry over medium low heat for 5 mins, or until carrot has started to soften.
Add flour to pan and cook, stirring for 2 mins. You will start to develop a nice brown layer on the base of your pan.
Add wine to pan and continue to stir for 1 min, scraping the layer from the based of the pan as you go.
Add garlic powder, ground sage, chicken stock and milk to pan, stirring well to incorporate and bring to simmer
Once simmering, cook uncovered over low heat for 10 - 12 mins, or until carrot is nearly cooked through. Mix through chicken.
Add chicken mixture to prepared baking dish (if using) and smooth the top. Top with the breadcrumbs, and bake for 15 - 18 mins or until casserole is bubbling and stuffing topping is golden.