Prepare the Raspberry Swirl: In a small saucepan, combine the raspberries with 2 tablespoons of the sugar. Warm over medium heat until the sugar dissolves, then let the mixture simmer gently for about 5 minutes, stirring occasionally. Once the berries have broken down and thickened slightly, strain the sauce through a fine mesh sieve into a bowl to remove the seeds. Discard the seeds and set the coulis aside to cool.
Create the Custard Base: In a heatproof bowl, whisk together the whole eggs, egg yolks, and the remaining sugar using an electric hand mixer until just combined. Set the bowl over a saucepan of gently simmering water—be sure the base of the bowl doesn’t touch the water. Continue whisking for 3 to 4 minutes until the mixture becomes thick, pale, and slightly increased in volume. Remove the bowl from the heat and keep beating until the mixture cools to room temperature.
Whip and Fold the Cream: In a separate mixing bowl, whip the double cream until soft peaks form. Carefully fold the whipped cream into the cooled egg custard using a spatula. Mix just until combined, being gentle to maintain the light texture.
Assemble and Freeze: Pour the ice cream mixture into a shallow, freezer-safe container. Drizzle the raspberry coulis over the top and use a skewer or knife to swirl it gently through the mixture, creating a ripple effect. Cover tightly with cling film and freeze for at least 6 hours, or overnight, until firm.
Serve and Enjoy: To serve, scoop the ice cream into bowls or cones. Garnish with fresh mango slices, extra raspberries, or colorful sprinkles if desired. Let sit for a couple of minutes at room temperature to soften slightly before serving for the best texture.