Preheat your oven to 350 degrees

Prepare a baking sheet with a silpat liner or with parchment paper

In a large bowl, mix together the butter and brown sugar

Add each egg one at a time and mix into the mixture

Add the vanilla and mix well until all of the wet ingredients are combined

Add in the flour, baking powder, baking soda, salt, and candy sprinkles; mix well until fully combined

Using a small ice-cream scoop, scoop dough onto the prepared cookie sheet - be sure to leave enough space for the cookies to expand while baking

Bake for 12 minutes

Allow the baked cookies to sit on the cookie sheet for 2 minutes before transferring to a wire cooling rack to finish cooling

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In a large mixing bowl, cream the butter

Add the vanilla and mix into the butter

Add the confectioner's sugar and incorporate well

Add the flour, half a cup at a time and mix well

Separate the butter cream frosting into 4 separate bowls

To each bowl of frosting, add the desired amount of food colouring agent

Mix each bowl of frosting separately until desired colour has been obtained

Add the frosting from each bowl into a prepared pastry bag with a large circular tip

Frost one side of one cookie and place another cookie on top; press lightly and form into a sandwich

Place the cookies on a baking tray and refrigerate for 30 minutes to set the frosting