Line a 9x5 inch loaf pan with plastic wrap. Use a couple small pieces of tape to stick the plastic wrap to the outside of the pan to prevent it from falling in on itself when you pour in the semifreddo. Set aside.

In a medium saucepan, cook the sliced strawberries with 1/4 cup of sugar over medium heat for approximately 6 minutes, or until the berries begin to break apart. Remove from heat and set aside.

Fill a large bowl with a couple of inches of ice water and set aside.

Using a separate medium saucepan, find a metal bowl that can rest inside the saucepan without touching the bottom. Add about 1 inch of water to the saucepan and bring to a boil. Reduce the heat to low-medium. Add the egg yolks, egg, and 1/4 cup sugar to the metal bowl, whisking until combined and pale yellow. Add the strawberry mixture and whisk to combine. Set the metal bowl over the saucepan and whisk constantly until the mixture is thick, approximately 3 to 4 minutes. Remove the bowl from the saucepan and set in the bowl of ice water. Whisk the mixture every so often until it is cool, approximately 3-5 minutes.

In the bowl of an electric stand mixer fitted with the whisk attachment, add the heavy cream and beat on medium-high speed until it forms soft peaks, approximately 2-3 minutes.

Fold the whipped cream into the strawberry mixture with a spatula until just combined. Pour the mixture into the lined loaf pan and smooth the surface.

In a small bowl, stir the strawberry jam and balsamic vinegar until well combined. Add drops of the jam mixture on top of the semifreddo mixture. You can either leave them as dollops or use a spoon to spread them out in swirls.

Cover the loaf pan with plastic wrap and freeze for at least 8 hours or overnight. Serve with sliced strawberries.