Preheat oven to 180 C / Gas 4. Line a 23cm springform cake tin with parchment.
Combine ground almonds, brown sugar and flaked almonds in a bowl. Add melted butter; stir with a fork until the mixture resembles wet sand. Spread on the bottom of the lined tin.
Combine apricots and water in a saucepan; bring to the boil and simmer until very soft, about 10 minutes. Drain; mash apricots into a pulp. Add amaretto; mix well. Sweeten with 1 teaspoon caster sugar.
Beat cream cheese, 150g caster sugar, 120g soured cream, cornflour and 1 1/2 teaspoons vanilla extract in a bowl using an electric mixer on low speed. Add eggs one at a time; mix well. Fold in 2 tablespoons of apricot pulp; reserve remainder for topping. Pour cheesecake mixture into the tin, covering the base.
Bake in the preheated oven until edges are puffed and surface of cheesecake is firm except for a small spot in the centre that will jiggle when the cake tin is gently shaken, about 45 minutes.
Beat 350g soured cream, 3 tablespoons caster sugar and 1 teaspoon vanilla extract together until combined. Remove cheesecake from the hot oven; spoon topping over the surface and return cheesecake to the oven for 8 minutes more.
Cool to room temperature, about 1 hour. Chill cheesecake in the fridge for 6 to 8 hours. Top with remaining apricot pulp.
Bake time is approximate as ovens vary; bake until the cheesecake is set.