Add the milk and 1/4 cup - 60g butter to a heatproof jug or bowl and microwave for 30 seconds or until butter is melted. Set aside to cool for 10 minutes.
To a large mixing bowl, add the sugar, flour and salt. Use a whisk to combine. Next, add the egg yolks and whisk together until smooth.
Add 1/4 of the warmed milk and whisk to temper the egg mixture. Whisk together before adding the rest of the milk. Mix until well incorporated.
Transfer to a medium sized saucepan and use a spoon or spatula to stir on medium heat until it thickens. Take off the heat and add half of the remaining butter and vanilla bean paste. Stir until the butter is melted and well combined. Then add the remaining butter and repeat.
Transfer the mixture to a medium sized bowl and cover with plastic wrap. Chill in the fridge for 2 hours. Once chilled, unwrap and use a spatula to smoothen out. Set aside in the fridge until ready to use.