Blend pineapple in blender until SMOOTH. It will look a bit foamy. Combine blended pineapple, sugar and corn starch in a saucepan and heat on med-high until it begins to bubble. Reduce heat go low and let simmer (stirring constantly) until sauce thickens, 3-4 minutes. Remove from heat and cool to room temperature. Placing the sauce in the refrigerator helps speed up the cooling process.
In a large mixing bowl combine butter, shortening, and sugar. Beat until fluffy. Turn mixer down and add egg, vanilla and pineapple sauce. Mix. Add baking powder. Sift in and flour and cornstarch and mix thoroughly for 1-2 more minutes.
Lightly flour your working surface and shape dough into a large ball.
Roll dough out to desired thickness (I usually do 1/4- 3/8″) and cut into shapes. Add flour to the dough if it feels too sticky but a nice soft dough is what you want. Carefully transfer cut out cookie shapes with a spatula to a baking sheet. Bake at 350 degrees for 12 minutes. Cookies will be soft. Let sit on baking sheet for 5 minutes before carefully moving to a cooling rack. Cool completely before frosting.
Whisk icing ingredients together and spread over cookies. Chill cookies until icing sets.
NOTE: You can add a tablespoon of lemon juice to cut some of the sweetness from the icing if you’d like.
Refrigerate leftover icing.
Video
Notes
If making giant 4″ cookies (like I did), this recipe will yield about 20 cookies. If making 3″ sugar cookies, it will make 30 cookies.