In a large mixing bowl, beat butter with an electric mixer until smooth. Then add sugar, baking powder, and salt. Mix until combined and smooth, scraping the sides occasionally.

Beat in egg, milk, and vanilla until evenly combined. Then beat in the flour until combined.

Divide dough in half and shape into discs. Cover/wrap dough and chill in the fridge for at least 30 minutes (to make it easier to handle).

Preheat oven to 375 degrees C.

On a lightly floured surface roll out half the dough at a time to a 1/4 inch thickness.

Cut into the dough with your favourite cookie cutter shapes. Keep gathering all the leftover dough together, shaping into a ball and rolling out again until all the dough is used up.

Place cut-outs on a parchment paper-lined baking sheet 1 inch apart and bake for 6-8 minutes. Edges should be firm and bottoms very lightly browned. While cookies are cooling on a wire rack, mix up the Vanilla Buttercream Frosting!

In a large bowl cream the butter using an electric mixer (or in a stand mixer) until smooth.

Add in the icing sugar, vanilla, and milk. Mix at low speed until icing sugar is incorporated and then mix at high speed for a minute or two. Buttercream should be lightened in colour and fluffy.

If it's too runny, mix in more icing sugar. If it's too stiff, add a TB of milk at a time until you reach the consistency you like.

If desired, divide buttercream into bowls and add gel food colouring. Feel free to just scrape the buttercream onto the cookie with a knife, or fill piping bags with buttercream and pipe fun designs onto the cookies!