https://www.bbcgoodfood.com/recipes/brandy-vanilla-butter

Based a sampling of recipes, the ratio (by weight) of butter to sugar can vary from 1:1 to 1:2 with brandy added tablespoons at a time to taste.

https://www.thespruceeats.com/easy-traditional-brandy-butter-recipe-435727

https://www.bbc.co.uk/food/recipes/rum_babas_served_with_48561

Recipe for rum babas via Paul Hollywood from Season 5(?) Episode1 "Cakes" of The Great British Baking Show.