Need to use buttercream on cookies: How can I make it so that it hardens, at least a bit.
If you use a simple buttercream using butter and powdered sugar, as opposed to a Swiss or Italian meringue buttercream, you'll have much better luck. The latter two can't harden because their sugars have been dissolved. But with a simple buttercream, the sugar doesn't dissolve completely, and will dry out leaving behind some hardened crystals that form the crust you're looking for.
or you could try royal icing
I use a recipe for Cookie Glaze from Land O' Lakes -- it's not buttercream, but it does harden to a shiny glaze, and is great for decorated iced cookies.
Ingredients 2 1/2 cups powdered sugar
2 tablespoons water
1 tablespoon LAND O LAKES® Butter, softened
1 tablespoon light corn syrup
1/2 teaspoon almond extract or vanilla, if desired
Combine powdered sugar, water, butter, corn syrup and vanilla in small bowl; mix until powdered sugar is moistened. Beat at medium speed until smooth, adding additional water, if necessary, to reach desired spreading consistency.
Glaze cooled cookies. Let stand until hardened (6 hours or overnight).
Recipe Tip. Nutrition Facts (1 tablespoon)Calories: 50
Dietary Fiber: 0g
Recipe #10148©1998Land O'Lakes, Inc.