For the ice cream: Take the ice cream out of the freezer and allow it to become soft.
Roughly chop the strawberries and add to a large bowl with the lemon juice. Let stand, stirring occasionally for about 10 minutes.
Fold the ice cream and the strawberries together and pour into a cling film lined 20cm tin. Freeze for at least 4 hours.
For the cake: Preheat oven to 175 C. Line the base of 2 x 20cm loose bottomed tins with parchment paper and coat with nonstick spray; set aside.
Whisk the flour, baking powder, salt, and 100g sprinkles in a bowl. Combine the buttermilk, oil, and vanilla in a jug.
In the bowl of a stand mixer, beat the sugar, butter, and light brown sugar on a medium speed until light and fluffy. Add the eggs one at a time, beating to combine between additions and occasionally scraping down the sides of the bowl. Continue to beat the mixture, until almost doubled in volume and very light and airy, which should take about 3 minutes.
Turn the mixer to low, then add the buttermilk mixture and beat until incorporated. Add the dry ingredients, and beat until just combined.
5. Scrape the batter into the prepared tins. Smooth the top with a spatula and sprinkle 2 tbsp sprinkles between the two cakes. Bake until the cake is light golden brown - a tester inserted into the center should come out clean - 30–35 minutes.
Remove cake from oven and cool on a wire rack.
To assemble: Remove the cakes from their tins and using a sharp knife slice off the outermost crust of the cakes to reveal the inside and it’s colours.
Remove the ice cream from the freezer and place one of the cakes on top of the ice cream.
Invert the tin and release the sides, removing the base of the tin and the cling film, then add the second cake circle on top.
Roll the whole thing in the remaining sprinkles.
Whisk the cream in a medium bowl with the icing sugar until soft peaks form, transfer to a piping bag fitted with a large star shaped nozzle and use to decorate the top of the ice cream cake, then serve in slices.