In a small saucepan, heat cream until bubbles form around sides of pan. In a small bowl, whisk the egg yolks, brown sugar and cinnamon. Remove cream from the heat; stir a small amount of hot cream into egg mixture. Return all to the pan, stirring constantly. Stir in maple flavouring.
Transfer to three 6-oz. ramekins or custard cups. Place in a 6-qt. slow cooker; add 1 in. of boiling water to slow cooker. Cover and cook on high for 2 to 2-1/2 hours or until centres are just set (mixture will jiggle). Carefully remove ramekins from slow cooker; cool for 10 minutes. Cover and refrigerate for at least 4 hours.
For topping, combine sugars and sprinkle over ramekins. Hold a kitchen torch about 2 in. above custard surface; rotate slowly until sugar is evenly caramelized. Serve immediately.
If broiling the custards, preheat broiler and place ramekins on a baking sheet; let stand at room temperature for 15 minutes. Broil 8 in. from heat until sugar is caramelized, 3-5 minutes. Refrigerate until firm, 1-2 hours.
Test Kitchen Tips
You can make these ahead. Top with sugar and caramelize right before serving.