Mix brown sugar, corn starch, and ¼ of the milk in a saucepan over heat. Whisk lightly until sugar and starch are dissolved. Add the egg yolks and cook, stirring constantly over medium heat until it thickens. When it resembles a pudding, add cold butter to lends your pudding flavor and gloss. Continue to whisk until the butter is melted.
Transfer to a different bowl to accelerate the cooling process. Mix occasionally to avoid curdling and let cool for thirty minutes. Whisk heavy cream with a hand mixer until it resembles whipped cream. Gently fold into the pudding mixture using a rubber spatula.
Crumble cookies into your cups and add a generous lump of pudding mixture. Line with a layer of strawberries, add another lump of pudding mixture and decorate the top with remaining strawberries.