Lightly grease and line the bottom and sides of a 9-inch square pan with parchment paper, leaving 1–2 inches of overhang for easy unmoulding.
In the bowl of a food processor fitted with the metal blade, combine the vanilla wafers, Redpath® Golden Yellow Sugar, orange zest, and salt. Pulse until mixture is a fine crumb size. Add in the melted butter and pulse a few times until crumbs are just moistened.
Transfer crumbs into the prepared pan. With a flat-bottomed glass or dry measuring cup, firmly press the crumbs evenly into the bottom of the pan. Place pan into the freezer to chill.
In a heavy-bottomed pot, combine the evaporated milk, the Redpath® Granulated Sugar, and salt. Place over medium heat and bring to a simmer, stirring until sugar is completely dissolved. Simmer for 5 to 7 minutes. Mixture should thicken slightly.
Remove half (approximately ¾ cup / 188 ml) of the mixture and transfer into a large bowl. In the pot, add the strips of orange zest to the remaining milk and heat; 1 minute. Remove from heat and transfer to another large bowl and place both bowls of evaporated milk into the fridge, uncovered, to chill completely; 30 minutes.
In the bowl of a stand mixer fitted with the whisk attachment (see Chef’s Tips), whip the heavy cream on medium-high speed until thickened. Add the vanilla extract. Whip until thoroughly combined; do not over-whip. Mixture should be between soft and medium peaks.
Remove the bowls of chilled evaporated milk from the fridge. Using a large rubber spatula, quickly fold in ½ cup (125 ml) of the whipped cream into the plain evaporated milk until fully incorporated. This lightens the mixture, making it easier to fold in the larger amount of whipped cream. Add in 1½ cups (375 ml) of the whipped cream and gently fold until just combined. Set aside in the fridge.
Remove and discard the orange zest from the other bowl of evaporated milk. Whisk in the orange juice concentrate and 2 to 3 drops of orange gel food colouring (if using) until well mixed.
Fold in ⅓ of the remaining whipped cream into the orange mixture until fully incorporated. Gently fold in the remaining whipped cream into the lightened mixture until just combined.
Remove the prepared pan from the freezer. Randomly pour or ladle ⅓ of the vanilla base into the pan, then randomly pour or ladle ⅓ of the orange base over and around the vanilla base. Repeat process until both mixtures are in the prepared pan. Run a rubber spatula or a spoon through them, swirling the two mixtures together but ensuring that they are not completely mixed. Place into the freezer.
After 30 minutes, remove from freezer and carefully lay a piece of parchment or waxed paper on the surface of the ice cream to prevent ice crystals from forming. Wrap well in plastic wrap and/or cover with foil. Place back into the freezer; at least 6 hours or until firm.
To serve, remove from freezer and allow ice cream cake to soften slightly; 5 minutes. Lift cake from the pan with the help of the parchment overhangs and place onto a cutting board. Carefully peel back the parchment paper.
Dip or run a sharp chef’s knife under hot water and dry with a clean kitchen towel. Slice into 16 servings. Serve immediately. Leftovers can be stored in the pan, wrapped well, or in an airtight container in the freezer for up to 2 weeks.
*Digestive cookies or any vanilla flavoured biscuits or cookies will work well in place of the vanilla wafers.
*Redpath® Dark Brown Sugar can be substituted for the Redpath® Golden Yellow Sugar in the crust. Note that there might be a subtle increase in caramel-like flavour in the crust.
*Redpath® Golden Yellow Sugar can be substituted for some, though preferably not all, of the Redpath® Granulated Sugar in the ice cream base. The slight caramel undertones of the Redpath® Golden Yellow Sugar may overpower the vanilla flavour, which is essential to the recipe.
*If a food processor is unavailable, place vanilla wafers into a large, heavy-duty resealable bag. With a rolling pin, roll over cookies until crushed fine. Transfer to a bowl and mix the remaining ingredients in by hand.
*Chill the bowl and whisk attachment used for whipping cream for at least 15 minutes before whipping. Cold heavy cream used straight from the fridge works best.
*Whipping the heavy cream to stiff peaks will result in ice cream with a fatty mouthfeel, which is why the heavy cream is whipped to between soft and medium peaks for optimal texture.