Preheat oven to 300°F. Place a piece of parchment paper on a baking sheet and use a large plate to draw a circle around it as a stencil for your meringue.
Whisk the egg whites with beaters for 1 minute until thick and foamy. Add cream of tartar and continue whisking on high for 3 minutes, adding the sugar 1/8 of a cup at a time every 30 seconds. Once the meringue is thick, fluffy, and holds a stiff peak, scoop the meringue onto the parchment paper to form a thick disk.
Put into the 300° oven and then reduce the temperature to 200° F. Bake for 1.5 hours, and then turn the oven off and leave in the oven for another hour.While the meringue is cooling in the oven, place berries in a saucepan on the stove, add sugar and Riesling, and simmer on medium for 10-15 minutes until a thick berry sauce is formed. Place in the fridge and allow to chill.
Pour heavy whipping cream into a bowl and add a quarter cup of sugar. With until thick and soft peaks have formed.
Once the meringue is finished place on a serving dish, top with a fluffy layer of whipped cream and gently pour cooked fruit over top, and serve!