Combine first 6 ingredients in a large bowl, stirring until sugar dissolves. Pour mixture into a shallow dish; freeze, uncovered, 3 hours or until firm. Flake ice mixture with a fork.
Shuck oysters, discarding top shells; run knife under meat of oyster to release. Place half shells on a serving platter lined with rock salt. Spoon 1 teaspoon mignonette ice onto each oyster; serve immediately.
*For testing purposes, we used Pinot Noir.
Note: To aid the shucking process, place oysters on a baking sheet. Bake at 350° for 15 minutes to open shells slightly.
Find a high-quality red wine vinegar when preparing this recipe. Lesser quality vinegars may taste harsh.