1/2 c. sugar
2 tbsp. cornstarch
1/8 tsp. salt
2 c. milk
1 c. half and half
1 egg yolk
1 tsp. key lime zest
1/3 c. key lime juice
1/2 c. coarsely chopped graham crackers
Whisk together first 3 ingredients in a large heavy saucepan. Gradually which in milk and half and half. Cook over medium high heat, stirring constantly, 8 to 10 minutes or until mixture thickens slightly. Remove from the heat.
Whisk egg yolk until slightly thickened. Gradually whisk about 1 c.hot cream mixture into yolk. Add yolk mixture to the remaining cream mixture., whisking constantly. Whisk in vanilla.
our mixture through a fine wire-mesh strainer into a bowel, discarding solids. Cool 1 hour stirring occasionally. Place plastic wrap directly on cream mixture; chill 8 to 24 hours.
Pour mixture into freezer container of a 1 1/2 quart electric mice cream maker and freeze according to manufacturer's instructions.
Stir in 1 tsp. key lime zest, 1/3 c. key lime juice and 1/2 c. coarsely crushed graham crackers halfway through freezing.
Let stand at room temperature 5 to 10 minutes before serving.
The worst part about this recipe is that it has to sit overnight before freezing. But it was worth the wait.