Step 1

Place chocolate and butter in a bowl set over a pot of simmering water and stir until melted and everything is combined; remove from heat and set aside. Place raspberries and 2 tablespoons of sugar in a blender or food process and pulse until pureed; set aside.

Step 2

Place eggs, egg yolk and sugar in a bowl set over a pot of simmering water and using a hand mixer beat until mixture is pale and thick (mixture should resemble cake batter), about 5-7 minutes. Remove from heat and continue to beat for another 4-5 minutes to cool mixture. (Optionally, you can place the bowl in an ice bath to quicken the cooling). Place heavy cream in a chilled bowl and using a hand mixer beat until soft peaks form. Add vanilla and beat until combined. Fold the two mixture together until combined.

Step 3

Pour 1/2 cup or more of semifreddo mixture into pan and spoon stripes of raspberry puree and chocolate on top. Continue to layer like this until all ingredients are used. Place in the freezer for 4-6 hours or until set.