- Preheat oven to 180C.
- For the Brioche Buns, place the flour, sugar and yeast in a bowl of a stand mixer fitted with a dough hook and mix briefly. Add 2 eggs, oil and 185ml water. Mix on high speed for 6 minutes, scraping the sides of the bowl occasionally. Add fine salt and beat for a further 1 minute to make a smooth but sticky dough. Portion dough into 6 balls and place on a lightly floured work surface.
- Knock the air from each ball of dough and gently roll to form a smooth ball. Place balls on a paper lined tray, leaving space between each. Lightly dust a large sheet of cling film and place over the balls to cover completely. Set aside, in a warm place, to rise until doubled in size, about 30 minutes.
- For the egg wash, place black and white sesame seeds in a small bowl, mix to combine and set aside. Place remaining egg and salt flakes together in a small bowl and whisk to combine. Brush the risen balls of dough with the egg wash and sprinkle with mixed sesame seeds. Place in oven and bake until the surface of the buns are golden, about 15-20 minutes. Remove from oven and while buns are still hot, brush lightly with melted butter. Set aside to cool until serving.
- To prepare salmon, place salmon in a deep bowl. Place sugar, salt and 1 litre of water in another bowl and stir to combine. Pour water mix over salmon and set aside in the fridge to cure for 30 minutes.
- Place a wire rack into the base of a lidded deep casserole dish. Remove salmon from cure and pat dry with paper towel. Place salmon onto rack and cover dish with cling film.
- Prepare smoking gun with hickory and apple woodchips, insert pipe under cling film and fill dish fully with smoke. Seal cling film and cover securely with a lid to trap smoke. Set aside in fridge for 25-30 minutes to infuse salmon with smoke.
- Remove infused salmon from fridge and slice into slices 2mm thick. Cover and set aside, in fridge, until serving.
- For the Pickled Onion, use a mandolin to shave onion into 1mm thick slices. Place slices in a vacuum resealable bag. Add lemon rind, oil, sugar and salt. Remove air from bag and seal. Set aside to pickle for 10 minutes then drain well and set aside until serving.
- For the Crème Fraiche, place all ingredients in a small bowl and mix together until smooth. Cover and refrigerate until serving.
- To serve, cut Brioche Buns in half. Spread Crème Fraiche over one half and top with 1 tablespoon drained Pickled Onions. Add 2-3 slices of Smoked Salmon, top with watercress leaves and finish with the top of the bun.