Put caster sugar in a saucepan, turn the fire on and let the sugar melt and become gold without touching or stirring.
When the caramel is done remove from fire and add warm milk cream, mix well and add soft butter little by little, always stirring.
Put the caramel into a bowl, be sure it's almost cool and add flour and brown sugar.Knead with a spoon and add the egg.Knead until you have a smooth loaf, wrap in cling film and let it rest in fridge for 20 minutes.
Make some rolls ( sausage like) out of the dough and let them rest in fridge, wrapped, for about 1 hour then roll them into brown sugar ( you can use milk or beaten egg to help sugar to stick, I had not this need) and slice them into thick cookies.
Put them on a baking tray and bake at 170°C/ 340°F for about 20 minutes.
Wait until cool before touching, they last about a week in a tin box.