FOR GELATO: In a bowl, stir together sliced apricots and lemon juice; let stand at room temperature 15 minutes.

Meanwhile, in a large heavy saucepan, combine milk and vanilla bean; bring just to a boil, then remove from heat and let stand 10 minutes. Remove and reserve vanilla bean for another use.

Transfer apricot mixture to a blender; add 1 tablespoon water, then purée until smooth.

In a medium bowl, whisk together egg yolks and sugar. In 2 additions, whisk in milk, then return mixture to saucepan. Bring mixture to a boil and cook, whisking constantly, 2 minutes; remove from heat. Transfer custard to a bowl; stir in purée and cream. Chill until cold, about 3 hours or overnight.

Freeze custard in an ice cream maker. Transfer gelato to an airtight container and freeze until firm enough to scoop, about 30 minutes or up to 1 day (gelato is best served fresh. Use it as soon as it is scoopable, when possible).

FOR CHOCOLATE-DIPPED APRICOTS: Line a large plate with parchment paper. Halve and pit apricots.
Fill a medium saucepan with 2 inches water; bring water to a simmer. Put chocolate in a medium heatproof bowl. Set bowl over (but not touching) the simmering water; stir until chocolate is melted. Dip 1 end of each apricot half about 1/2-inch into the chocolate, then, cut-side up, place on prepared plate. Refrigerate until chocolate is set, about 5 minutes.

Arrange prepared apricots, cut-side up, onto a serving plate. Put scoops of gelato into apricots. Serve immediately.