12 oz (350g) butter, curt into small pieces
2lb (900g) sugar (it says castor, I have used granulated)
Thinly pared rind and juice of 6 large (unwaxed) lemons
8 eggs, beaten
Place all ingredients in a heatproof bowl placed over a saucepan of boiling water or in the top of a double boiler. Cook, whisking gently until the butter has melted and the sugar has dissolved. Pour the mixture through a strainer placed over a bowl. Discard the lemon rind. Return the mixture to a clean heatproof bowl or top of the double boiler. Cook, stirring frequently, until the mixture thickens (about 40 mins). Pour into clean, dry, warm bottles (I assume it means jars) up to the rim. The yield will be about 3lb (1.35kg). Cover and label. Store in a cool place.
Should be used within 3 to 4 months.