To make the dough, combine the ingredients and mix in an electric mixer, using a dough hook, until a smooth dough forms and all the butter has been fully incorporated. Cover with Clingfilm and leave to prove for one hour.
Portion the dough into eight 50g balls. Place the balls on an oiled baking sheet and cover with a clean tea towel, leave to prove for another hour at room temperature.
In a heavy-bottomed pan brown the venison mince over a high heat then add the garlic, shallots, thyme, rosemary & fennel. Once the meat has caramelised and the veg has softened, add the tomato purée and continue cooking for a minute. Add the Sherry and stock, season and reduce the heat to a simmer. Reduce until a thick consistency is achieved. Set aside and leave to cool.
In a small pan, gently simmer all the ingredients for the bramble sauce until the sugar has dissolved and the berries have broken down. Continue reducing until it has thickened to the consistency of ketchup. Pass the sauce through a fine sieve into a dipping dish (or to take the dish to the next level, fill pipettes with the sauce and skewer into the centre of the buns so that guests can squeeze themselves!).
Once the dough balls have almost doubled in size and the mince mixture has cooled to room temperature, fill each dough ball with 40g of venison, pinch the edges to reform the ball shape and generously sprinkle smoked sea salt over the top.
Using a bamboo steamer, place the buns over a pot of boiling water and steam for 11 minutes. Serve immediately.