Panna cotta is a custard, but while many custards thicken around the egg protein albumen, this one thickens around the gelatin protein collagen. Like other gelatin containing desserts, it should be prepared several (at least 4) hours ahead of time so that it can fully thicken.
Ingredients-- the panna cotta itself
3 cups heavy cream
1 cup half and half
1/4 cup sugar
1 tablespoon vanilla extract
2 teaspoons unflavored gelatin (measure from contents of 1 packet)
1/4 cup cold water
a pinch of salt (about 1/3 of a 1/8 teaspoon measure, if you desperately need to be told a specific amount)
Ingredients-- balsamic reduction topping
1 cup balsamic vinegar
2 tablespoons raisins
1 cup boiling water
Step 1: Start making the cooked cream
Measure 1/4 cup of water into a broad bowl (I used a cereal bowl, see picture) then sprinkle gelatin on its surface and let sit.
In a large sturdy pan, mix cream, half and half, salt, and sugar. Stirring, bring to a simmer over moderate heat.