1. To make ice cream: In a bowl, whisk egg yolks with sugar until thickened and pale yellow. Set aside.
2. Slit vanilla bean lengthwise and scrape seeds into a medium saucepan. Add vanilla pod, milk and cream. Place saucepan over medium-low heat and bring milk mixture just to a simmer. Remove from heat. Let stand for 15 minutes, allowing the flavor of the vanilla to infuse.
3. Discard pod. Bring to a simmer over medium-low heat and simmer for 5 minutes. Gradually whisk into the egg mixture.
4. Return entire mixture to the saucepan. Cook over low heat, stirring constantly, until the mixture is thick enough to coat the back of a wooden spoon. Be careful not to let it boil. Strain into a clean large bowl. Let cool to room temperature. Cover and refrigerate until completely cold or overnight.
5. Stir cream mixture. Transfer to an ice cream maker and freeze according to manufacturer's instructions.
6. To make Crackled Caramelized Sugar Topping: In a medium saucepan, stir together sugar, water and corn syrup. Bring to a boil. Cook over medium heat, brushing down the side of the saucepan wtih cold water occasionally, until candy thermometer registers 300 degrees F or mixture turns golden brown.
7. Carefully pour onto prepared baking sheet. Let cool completely. Break into shards. Set aside.
8. When ready to serve, place two scoops of ice cream in a bowl and top with crackled sugar.