Preheat the oven to 180°C/350°F/Gas 4. Line a 9x13 baking pan with parchment paper and set it aside.
Using an electric handheld or standing mixer, beat the butter, sugars, eggs, and vanilla until combined and creamy.
Sift or whisk the flour, baking soda, and salt into a large bowl.
Gradually mix the dry ingredients into the wet until combined and a dough has formed.
Press the dough into the prepared pan and bake in the oven for 35-45 minutes or until a light golden color.
Leave to cool in the pan for 10 minutes before turning out and cutting into 12 bars.
Transfer to a wire rack to cool completely before decorating.
Using an electric handheld or standing mixer, beat the butter, powdered sugar, vanilla, and cream until combined, smooth and holds a peak.
Scoop the frosting into a large piping bag fitted with an open star tip (Wilton 1M).
Pipe a zigzag line across the top of the cookie bars to cover.
Add sprinkles on top.
Allow the frosting to harden slightly before serving.
Enjoy and Happy Easter!