Line the base of a loaf tin (22cm x 12cm / 9-inch x 5-inch) with cling film.
Place the double cream in a large bowl and whip it with a hand mixer until stiff peaks form, about 4 minutes.
Once ready, using a spatula gently fold the condensed milk into the whipped cream. Drizzle the chocolate over the mixture, then sift the cocoa powder in, add the California Walnuts and gently stir until all the ingredients are combined.
Pour the semifreddo mixture in the prepared loaf tin, and smooth the surface. Cover with cling film and freeze for 4-5 hours or overnight.
Remove the semifreddo from the freezer 10-15 minutes before serving. To serve, unwrap the loaf tin, place a serving platter over the tin, and turn the semifreddo upside down onto the platter.
Decorate with fresh strawberries, chopped chocolate and California Walnuts, and serve.
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Notes
Chop the chocolate into little chunks and melt it over a bain-marie or in the microwave at 30 seconds intervals.
Leave the fresh heavy cream in the refrigerator right up until you're ready to whip it.
Feel free to skip or reduce the amount of icing sugar if you’re using sweetened condensed milk.
To make the semifreddo super airy and mousse-like, you can slightly whip the condensed milk to incorporate as much air as possible.
Make sure the melted dark chocolate is completely cool before you add it to the semifreddo mixture.
Remember to sift the cocoa powder before adding it to the mixture.
Make sure you stir the ingredients slowly and gently.
Brush with butter the loaf pan, then line it with cling film so it doesn't move around.
To easily slice the semifreddo, dip a sharp knife in hot water for a few seconds, then slice.