Step 1Melt semisweet and unsweetened chocolate in top of double boiler set over, but not touching, simmering water. Add 1 cup hot Custard Ice Cream Base. Stir well, then whisk into remaining Custard Ice Cream Base. Strain into medium bowl and place in freezer until well chilled, stirring occasionally, about 1 hour.
Step 2When ice cream mixture is cool, place in ice cream maker and freeze according to manufacturer's instructions. Immediately line 2-quart mold or bowl with 3/4 to 1 inch of ice cream, using spatula or spoon dipped in warm water if necessary, and place mold in freezer 2 to 24 hours.
Step 1Place apricots, 1 tablespoon sugar and lemon juice in bowl of food processor or blender and puree until smooth, about 2 minutes. Strain and set aside.
Step 2Combine water and 1 cup sugar in small, heavy saucepan and boil over medium-high heat until clear, 5 minutes. Remove from heat and let cool.
Step 3Stir egg yolks and apricot puree into syrup. Return to medium heat and whisk until thickened, 2 to 3 minutes, then remove from heat and beat until cool.
Step 4Whip cream until it forms stiff peaks, then fold into apricot-egg yolk mixture. Fill interior of ice cream-lined mold with mixture, cover with plastic wrap and set in freezer until solid, 2 to 3 hours.
Step 5Remove plastic wrap and dip bowl in hot water until bombe is loosened. Place serving plate upside down on top of mold; holding mold and plate together, invert so that bombe drops onto plate. Smooth surface with spatula and return to freezer for 1/2 hour or more to firm up.