Season cavity, place 1 rosemary sprig and 1 of the garlic pieces inside.
Mix wine, stock powder, balsamic, crushed thyme & sauce (gently heat to melt if using a jam type sauce, like cranberry)
Place bag in slowcooker & lay in thick sliced onion
Season outside of pigeon and rub over the sauce mix place in oven bag, on the onion
Spoon over the rest of the sauce
Tie bag and cook on low for 6-8hrs
Remove pigeon carefully, break up or serve whole
If you like, pour off sauce and onion into slowcooker bowl, add in broken up pigeon, if whole pour over some sauce
Serve with vegetables or salad
Leftover meat can be shredded, moistened with some of the sauce and used as a pie filling etc