Melt quince paste with the water and lemon juice in a small saucepan over low heat, stirring until the mixture becomes smooth and lump-free. Take care not to burn the paste. Set aside.
Preheat fan-forced oven to 220°C.
Season the cavity of each quail with salt and pepper. Divide breadcrumb mixture equally between the quail and carefully fill each cavity. Tuck wings underneath the quail. If you want to, you can secure the quail legs together with a toothpick or tie with kitchen string. Season quail with salt.
Heat the 50g of butter in a clean large frying pan over medium heat, then, when it’s foaming, add quail to the pan and gently brown on all sides. Place the quail on a baking tray, breast-sides up, then brush the quince glaze generously over each quail; if the glaze is too hard to spread, then gently reheat it over low heat.
Roast the quail for 10–12 minutes or until cooked through; do not overcook. Leave to rest, breast-sides down, in a warm place for 10–15 minutes before serving.