Combine the lemon juice and pear in a medium saucepan, cover and simmer over a medium-low heat for 20 minutes, stirring occasionally. Transfer to a food processor and purée until smooth. Transfer to a mixing bowl and combine with the brandy.
Bring the cream to the boil in a small saucepan over a medium heat. Remove the heat and allow to cool.
Meanwhile, whisk together the egg yolks and the caster sugar until thick and pale. Gradually whisk in the hot cream over the egg yolks and then return to the saucepan. Cook over a very low heat for 15 minutes, stirring with a wooden spoon until it coats the back of the spoon.
Strain the thickened mixture into the pear purée and mix until smooth. Allow to cool, then cover and chill for 2 hours. Churn in an ice machine until thickened and frozen. Allow two scoops per serving and serve in glasses.
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