Shortbread cookies with Icing cookies - Eggless cookies recipe - Kids friendly

Merry Christmas! Shortbread cookies is one of my kids most favourite cookie recipe. So far I haven't tried icing before. I always had this misconception that icing requires more sugar and would be very sweet. So I had been avoiding it even after multiple requests from my kids. After I saw one of the videos I realised that the amount of sugar can be controlled. It is also very colourful and attractive. I have followed basic shortbread cookie recipe.

All purpose flour - 1 cup (125g)
Salt - 1/8 teaspoon
Butter - 1 stick (1/2 cup) (57g)
Powdered Sugar - 1/2 cups (100g)
Vanilla extract - 1 teaspoon
For icing 
Icing sugar – 1 cup 
Food colour – as needed 
Vanilla essence – 1/2 tsp Milk – 2 tbsp 

Shift the flour and salt together. Keep it aside..In broader bowl take butter, Vanilla extract and icing sugar and beat it till it is creamy and smooth. Scrap the sides as required. 
Now add Flour and bring together with your hands into stiff dough. Add a teaspoon of milk of required.
Wrap the dough in plastic wrap and keep it in refrigerator for an hour. Line the baking tray with parchment paper. Take out the dough and roll it into 1/4 inc thick circle. Using the desired shape of cookie cutter prepare the cookies. 
 Arrange the cookies in the baking tray. Pre-heat the oven at 180 degree C. Bake the cookies for 10-12 mins or till the cookies are slightly browned. Cool it completely 
Mix in Powdered sugar, vanilla essence, milk. It will be in running consistency but thick
Diviide it into no of colors you want to have. Add desired food color and mix well.
Fill it in zip lag or any plastic cover. Make a small hole in one corner. 
Draw the line like shown in the pic. Then you start to fill the center.
Store it in air tight container and enjoy it