Pre-heat your oven to 240 degrees C. Warm your milk in a small pan until steaming (not boiling). Take off the heat for now.
Rub your unsalted butter (cubed) into your strong flour until a breadcrumb-like consistency is achieved.
Whisk an egg into the milk once it has cooled down a little.
Stir half your sugar (40g), pinch of salt and yeast into the flour mixture. Make a well in the middle of the flour and pour in the egg/milk mix. Mix together using a kitchen stand mixer and a dough hook, until a dough has formed. Mix for 5 minutes more.
Once the dough is smooth and springy, place into an oiled bowl (I used the same one) and cover with a damp tea towel (just run under the water and squeeze out the excess). Place in a warm place to rise until doubled - this will take about an hour.
Once proved, knock back by pushing your hands down on the inflated dough and turn out onto a floured surface. Divide into 6 equal pieces. Shape into balls and place on a lined baking tray. Prove again, covered, until doubled in size. This may take 30 -45 minutes.
Make an egg glaze by whisking together an egg and 2 tbsp of milk. Brush over the proved buns. Bake in your oven for 20 minutes, until brown.
Whilst the buns bake, make your sugar syrup glaze by boiling 40g caster sugar and water in a pan, until the sugar has all dissolved. Once the buns come out of the oven, brush the warm syrup over the buns. Sprinkle on your crushed sugar cubes (I used the end of a rolling pin to crush mine).