In a large bowl, pour in the whipping cream and beat with a hand mixer to soft peaks.
Pour in the condensed milk and orange zest and whisk again until fully mixed together.
Put 20 amaretti cookies into a Ziploc bag and break up in medium pieces. Pour cookies into the cream and with a spatula, fold the cookies into the cream.
Line a loaf pan with plastic wrap. Pour cream mixture into the pan. Cover with the plastic wrap and freeze overnight.
When ready to serve, remove from the loaf pan and remove the plastic wrap. Place on a serving platter for 10 minutes before cutting into it.
Put the remaining 10 amaretti cookies into the Ziploc bag and crush into small pieces. Sprinkle on top of the semifreddo to garnish.
