Preheat the oven to 180 degrees. Grease and line a 18 cm x 28 cm slice tray with baking paper. Place the butter and chocolate in a microwave safe bowl. Heat for 30 second bursts for 3-4 minutes(until melted), stirring with a dry metal spoon between each burst. Add the brown sugar and mix until combined. Allow the chocolate mixture to cool slightly.
Beat the eggs in a separate bowl until light and fluffy. Add the eggs and vanilla extract to the chocolate mixture and whisk together well. Add the plain flour and the milk chocolate chips and fold through gently. Pour the mixture into the prepared tin and bake for 25 minutes or until a skewer inserted into the middle comes out clean. Set the brownie aside to cool and then place into the fridge for at least 3 hours (preferably overnight).
Remove the brownie from the fridge and use a round shaped cutter to cut out circles.
Wash, dry and hull the strawberries and add one to the top of each brownie circle.
Whip the thickened cream and the caster sugar with beaters on high until stiff peaks form. Place the whipped cream into a piping bag(or a ziploc bag with the end snipped off), and pipe around the edges. Then pipe a small dot on top of each strawberry.
Place the Santa brownie hats into an airtight container in the fridge until required