Place cornstarch in a small saucepan. Gradually add milk, stirring with a whisk until blended. Stir in coffee. Cook over medium-high heat 1 minute or until mixture just begins to simmer. Remove from heat; stir in chocolate chips. Cook, stirring constantly, over medium-high heat until mixture comes to a boil; cook 1 minute until mixture is smooth and slightly thickened. Remove from heat; stir in powdered sugar, cinnamon, and vanilla extract.
Spoon 1/2 cup ice cream into each of 8 dessert bowls. Top each serving with 2 1/2 tablespoons sauce and 1/2 tablespoon pine nuts.
Cornstarch is ideal for making quick sauces because it thickens liquids much faster than flour. Be sure to remove the sauce from the heat after it has thickened; if it cooks too long, the cornstarch will lose its thickening power, causing the sauce to separate and become thin.