Preheat the oven to fan 140C/conventional 160C/gas 3. Tip all the ingredients for the base, except for the egg, into a food processor and blend until like breadcrumbs. Add the egg and blend again to make a paste. Scrape onto the base of a greased 24cm loose-bottomed springform tin, spread with a spatula then bake for 25 minutes until risen
and just set.
Meanwhile beat the ricotta in a bowl with the eggs, soured cream, sugar and vanilla, then when the base has had its 25 minutes, take it out of the oven. Quickly scatter the apricots over the base and pour the cheese mixture on top. Return to the oven for 50 minutes more until the mixture has set and is starting to turn golden round the edges.
Run a knife round the cake to release it from the sides of the tin then cool and chill. You can make this a day ahead.
Transport the tin covered with cling film or foil, then turn out and dust with icing sugar when you get there.