Melt the butter in a large mixing bowl, using 15 second microwave bursts.
Add the soft brown sugar. Whisk to combine.
Add the eggs, Baileys and vanilla. Whisk again.
Sift in the flour and baking powder. Mix together until smooth - the batter should be quite liquid.
Add the white chocolate chips. Fold together.
Spoon into a lined baking tray.
Bake for 24-26 minutes until firm at the edges and a little under in the centre - it will continue to set as it cools.
Allow to cool in the tin for 10 minutes, then carefully turn out onto a wire rack to cool completely. To do this, I find it easiest to grab a *light* board (important so you don't squash the blondies!). Put the board on top of the blondie tin, then hold the tin underneath and turn the whole thing upside down, allowing the blondie to drop onto the tray/board. Peel off the paper, then place the cooling rack on top of the blondies and, holding the board underneath, flip again so that the blondie sits safely on the rack.
Make the Baileys icing
Wait to make the icing until the blondies are completely cool.
Sift the icing into a small bowl and add the Baileys.
Mix to a smooth paste. If it's too thick to drizzle, add more Baileys a drop at a time. Using a small whisk or the back of your spoon to remove out any lumps.
Drizzle the icing over the blondies.
Allow to set, then transfer to a board.
Slice into large, decadent squares in a 3 x 4 pattern.
Video
Notes
These Baileys blondies should be stored in a sealed container to keep them fresher for longer and prevent them from drying out.If you need to stack them, be sure to let the icing drizzle set first, then place a little greaseproof paper between layers so that they don’t stick together.Store the container in the fridge.If stored correctly these Baileys blondies should stay fresh for up to a week. Alternatively, you can freeze them for up to three months.