Bring stock to the boil in a saucepan over high heat

Meanwhile, melt butter in a saucepan over medium heat. Add flour. Cook, stirring, for 1 minute or until mixture bubbles. Gradually stir in 1/2 cup stock. Cook, stirring, until

Mixture is smooth. Repeat with remaining stock, 1/2 cup at a time. Cook, stirring, for 5 minutes or until thickened.