Sea-salted caramel tart with Javanese milk chocolate

200g of Javanese 40% milk chocolate, broken into pieces

200g of light muscovado sugar

1 tsp flaky sea salt

150g of golden caster sugar

4 egg yolks

500g of plain flour

50g of cacao nibs, cracked

550g of butter, softened

200g of double cream

50ml of water