Place flour and milk into the Thermomix bowl and blend 5 sec/speed 6. Cook 10 min/80°C/speed 4. Pour into bowl, cover with plastic wrap, pushing plastic down onto surface of mixture. Cool completely.
Place sugar, 30g of butter, salt, brandy and vanilla bean paste and chop 5 sec/speed 7. Cook 10 min/Varoma/speed 2. Remove from heat and cool completely.
Place cooked milk paste or roux, cold caramel and remaining butter into the Thermomix bowl and blend 6 sec/speed 6.
Insert Butterfly. Beat 1 min/speed 4 until very smooth. Cover and refrigerate for 15 minutes. Use immediately. This frosting cannot be made ahead of time, but you can make the roux and caramel ahead if you need to.