1: Mix the cream and sugar together in a saucepan over a high heat and bring to the boil, stirring to dissolve the sugar. Turn the heat down to a simmer and stir for 1–2 minutes until the bubbles are quite large. Add the lemon juice and whisk thoroughly.
2: Pass this mix through a fine sieve into a bowl and leave to cool for about 5 minutes. Skim off any air bubbles, then pour the posset into your serving glasses. Leave to cool completely, then place the bowls in the fridge for at least 2 hours.
3: To make the biscotti, preheat the oven to 170°C/Gas Mark 3 and line a baking sheet with baking parchment. Sift the flour and baking powder together and leave to one side until needed. Beat the sugar and butter together in a large bowl until light and creamy. Beat in the eggs, one by one. Stir in the flour mix, then fold in the almonds and the fennel seeds.
4: Divide the dough in half and shape into 2 logs, each about 20cm long and 10cm wide on the baking sheet. Place the baking sheet in the oven and bake the biscotti for 20–25 minutes until golden brown. Remove the baking sheet from the oven and leave the baked dough to cool on the baking sheet for 10 minutes. Do not turn off the oven. After 10 minutes, slice both pieces of baked dough widthways into biscotti, 1–2cm thick.
5: Lay the biscotti on to a wire rack that will fit in the oven. Return them to the oven on the wire rack and bake for a further 5 minutes, or until they are crisp and dry. Remove them from the oven and immediately dust with icing sugar. Leave the biscotti to cool completely, then store them in an airtight container for 3–4 days.
6: When the lemon posset is set, serve it with biscotti on the side.