These buns don’t actually have any added pineapple, the name comes from the shape the top of the buns have.

Ingredients
400g strong bread flour
70g caster sugar
½ tsp salt
7g (1 sachet) fast-action dried yeast
25g butter, cut into small cubes
125ml warm water
75ml warm milk
1 tbsp vegetable oil
1 egg

Ingredients for the topping
200g  butter
200g caster sugar
1 egg
1 tsp vanilla paste or extract
200g plain flour
200g self-raising flour

Method
Put the bread flour in your stand mixer and to one side put the sugar and salt and on the opposite side, put the yeast.  Put the butter on the top, add half of the warm water and all of the warm milk and start to mix at a low speed. Gradually pour in more of the warm water until the flour has all been picked up by the mixer - depending on humidity, heat and the flour, you may not need it all. Turn the speed up to medium and knead for around 7-10 minutes until the dough is smooth and elastic. 

Take the dough out of the bowl and rub 1 tsp of oil around the edge of the bowl.  Fold the dough into one large ball and put back into the mixing bowl.  Cover with cling film and put the bowl somewhere warm to prove for 1-2 hours until double in size.

Once the dough has doubled in size, knock it back by punching into it and shaping it into a rough ball once more, then cover and put to one side to prove again for a further 30 minutes, or until doubled.

Once the dough has doubled in size once more, take the dough and divide into 10 equal pieces.  Roll each piece of dough into ball place on a baking tray lined with a silpat liner or greaseproof paper.

Once all the buns have been made, cover once more with clingfilm and leave to prove for a further 30 minutes.

Preheat the oven to 180c.

During this third prove, make the topping.  In a stand mixer, whisk the butter and sugar together until light and fluffy. Add the egg and whisk in well.  Once the egg has been well combined add the vanilla extract and the flours into the bowl and on a medium speed, mix all the ingredients together.

Remove the cookie dough from the bowl and roll out on a floured surface to about ½ cm thick.  Using an 8-9cm cookie cutter, cut the  topping into 10 rounds to cover the buns. Use the back of a blunt knife to gently make a criss-cross pattern on each crumble top, making sure you do not to cut through completely.

By the time you've finished your topping, the buns should be ready.  Beat the egg yolk and 1 tsp of water together and brush the top of each bun with the egg wash and carefully place a crumble top on each of the buns. Brush a coat of egg wash over the crumble top and bake the buns in the oven for 15-20 minutes, until the top of the crumble is beautifully golden brown.