Line a 9 by 5 inch loaf pan with plastic wrap, with a 2-inch overhang.
Puree the strawberries (reserving several nice ones) with the orange juice and 2 tablespoons of the sugar. Chill the puree.
Fill the bottom of a saucepan or double broiler with water and bring to a low boil.
Use a glass bowl or the top of the double broiler and beat the eggs with the remaining sugar, milk and vanilla.
Place over the simmering water and whisk for about 10 minutes, until it thickens and forms ribbons. Cool in the refrigerator for 1 1/2 hours.
When the egg mixture has cooled, whisk in the mascarpone and all but 1/4 cup of the strawberry puree.
In a clean dry bowl whip the cream until firm peaks form. Fold the cream into the strawberry-mascarpone mixture. Pour into the pan and freeze for 4 hours. Place the reserved puree in the refrigerator.
Unmold the semifreddo by pulling on the plastic wrap, then invert the pan onto a serving platter. Slice or leave whole the strawberries and add to the puree, or place on the side of the serving.