In a saucepan, combine strawberries, sugar, water, and lemon juice over medium heat. Bring to a simmer and cook for about 8 minutes or until strawberries start to break down and soften. Remove from heat and mash slightly with potato masher. Let cool.
Place chocolate in a bowl set over saucepan with barely simmering water to melt. Whisk in cream and butter until smooth and glossy. Remove from heat. Whisk in egg yolks, one at a time, stirring well after each addition. Whisk in icing sugar and rum until well combined. Pour chocolate mixture into non-stick 8x4 inch (1.5L) pan and drop pan to even out and remove air bubbles. Cover with plastic wrap and freeze for at least 6 hours or overnight, or until firm.
Remove plastic wrap from top of loaf and turn out onto serving platter. Slice or alternatively, leave in pan and scoop into bowl. Serve with strawberry sauce and whipped cream, if desired..
Tip: Semi Freddo can be frozen for up to 2 weeks.