Preheat the oven to 300° and position a rack in the center of the oven.
Draw an 8-inch circle on a sheet of parchment paper and invert it on a baking sheet.
2. In the bowl of a standing electric mixer fitted with the whisk, beat the egg whites, salt and cream of tartar at medium-high speed until soft peaks form.
Gradually beat in the sugar at high speed until the whites are stiff and glossy, 3 minutes.
Beat in the vanilla and bourbon.
Add the cocoa nibs and beat until just incorporated.
Spread the meringue on the paper in an 8-inch round.
3. Bake for 1 hour and 10 minutes, until the surface is dry and lightly browned and the center is still a bit soft.
Let cool completely on the baking sheet, 30 minutes.
4. Transfer the Pavlova to a board.
Drizzle with the chocolate and top with the raspberries.
Cut the Pavlova into 8 wedges and serve.
Cocoa nibs are available at specialty food shops.