In a small pan, add the coffee to the sugar, mix and bring to the boil. Stir occasionally to prevent sticking to the bottom of the pan.
Put the egg yolks in a heatproof bowl and whisk lightly. Add the syrupy coffee mix a little at a time, vigorously whisking to prevent the yolks from curdling. Set the bowl above a pan of simmering water, ensuring that the bowl does not touch the water. Stir and cook till the mixture gets thick and creamy.
Put the creamy egg mixture in a mixer and whip until it cools. Whip in the mascarpone cheese.
Whip the whipping cream to semi-stiff peaks. Add two spoonfuls of the whipping cream to the coffee mixture and stir in to make the mixture creamier. Add in the rest of the whipping cream and mix gently, making sure you don't deflate the cream.
Add the caramelised crushed walnuts to the creamy egg and coffee mixture. Pour this mixture into 4 serving or ice cream glasses and place them in the freezer for at least 5 hours.
Serve the coffee parfaits garnished with extra whipped cream, some chocolate pieces and crushed biscuits.
Take out the parfaits about 10 minutes before serving, allowing them to soften a little.
Follow the instructions carefully as you don't want any lumps, I have now made this twice & it's fabulous. You can ( like I did ) use cocoa instead of coffee & everyone loved it. Thanks for sharing. - 11 Jan 2016