Preheat the oven to 200C or 180C Fan or 400F or Gas 6
In a pan, gently melt the butter, add the onions, and cook for 8-10 minutes over medium heat until the onions soften.
When the onions are done, stir through the sage and cook for another minute,
Add the breadcrumbs and sausage meat and combine well.
Add the chicken stock and stir to combine. Add a little more as necessary, depending on the texture. If it's too wet, add more bread crumbs; if it's too dry, add more liquid.
Line a baking tray with parchment paper. Roll the stuffing into 16 equal sized balls and arrange on the lined baking tray.
Bake in the centre of the oven for 18-20 minutes until crispy and cooked through. The balls should read 75C using a temperature probe.