My shortbread recipe

Ingredients
230 grams unsalted butter
175 grams confectioner’s {icing} sugar
1 egg {room temperature}
1.5-3 teaspoons extract or emulsion {any flavor}
1 teaspoon salt
400-425 grams all-purpose flour

*** Important  : don't use any leavener or acid ! ***

Cream together butter and sugar.
Add eggs and extract and mix well.
Sift together flour and salt, add to wet mixture little by little until well incorporated.
Roll, emboss and cut cookies into desired shapes, dusting with flour as necessary.
Bake cookies at 200 Celsius for 7-8 minutes until tops are appear dry rather than shiny.

The secret is to pre -heat well the oven, and apply the right amount of pressure on the dough. 

I've made thousands of cookies with this recipe so I can guarantee it works !