For the toast, preheat the grill to a medium setting.
Grill the sourdough slices for 1-2 minutes. Turn over and drizzle with olive oil. Sprinkle over the crushed juniper berries. Toast for 2 minutes or until golden-brown. Keep warm.
For the dressing, blend all of the dressing ingredients to a smooth purée in a food processor. Set aside until needed.
For the remoulade, peel the celeriac and cut the flesh into thin strips, sprinkling the strips with salt as you go to prevent it from discolouring and to absorb any moisture. Set aside for 3 minutes.
Wash the julienned celeriac under a cold running tap, then drain. Transfer to a large mixing bowl. Stir in the mustard and crème fraîche until well combined. Chill in the fridge until needed.
For the venison tartare, in a bowl, mix together the diced venison, shallot, parsley and cornichons. Pour over the dressing and mix until well combined, Season, to taste, with salt and freshly ground black pepper, then mix again.
To serve, place one ring mould onto each of 4 serving plates. Divide the venison tartare equally among the ring moulds, pressing the meat down into the sides of the mould. Twist a helping of the celeriac remoulade around a fork and place it alongside the venison. Add a slice or two of toast and top each venison tartare with a half eggshell containing a quail egg yolk. Finally, garnish each plate with the chestnut slices.