Earl Grey Sugar Cookies with Citrus Frosting

For the cookies:
Preheat oven to 175ºC (350ºF). Line 2 to 3 baking trays with baking paper. Set aside.

In a medium bowl, mix flour, baking powder, baking soda, salt and ground Earl Grey tea leaves. Set aside.

In a large bowl, beat together room temperature butter and caster sugar with an electric mixer until pale and smooth. Add sour cream, vanilla extract and egg, mix well.

Gently, in small increments, add flour mixture into butter mixture whilst beating with an electric mixer. Mix thoroughly.

Take large 1/2-tablespoon-sized chunks of sugar cookie dough and form into balls with your hands. Coat your hands with flour if dough is too moist and sticks to your hands. Place each ball on the lined baking tray and gently, with your fingers, evenly flatten a little bit. Leave around 1½ cm between the cookies.

Bake on the middle rack for 10 minutes or until cookies are on the brink of turning golden brown from the rim. The cookies should appear a tad under-baked, so they will be pale. With care, transfer to a cooling rack. Leave to cool completely before frosting.

For the frosting:
Beat room temperature butter and icing sugar with an electric mixer until blended. Gradually add citrus juices. If frosting starts getting too liquid, add more icing sugar. Beat until smooth and fluffy.

Add 1 1/2 teaspoon grated orange zest and 1/2 teaspoon each lemon and lime zest. Beat until throughly mixed.

Mix remaining orange, lemon and lime zest together. Set aside.

With a knife, evenly top each cookie with thick layer of the citrus frosting. Sprinkle reserved orange, lemon and lime zest as garnish. Let stand at least 2 hours for frosting to harden.

Store in the refrigerator.