Preheat the oven to 350°F
Line a 12x17 inch pan with parchment or foil leaving overhang on the sides
In a bowl combine flour brown sugar cornstarch and salt
Cut in the butter until coarse crumbs form
Add water and egg yolks and mix until dough comes together
Add a little more water if needed
Press the dough evenly into the bottom of the pan
Do not press up the sides
Poke holes across the crust with a fork
Bake for 20 to 22 minutes until golden brown
Remove and cool completely
In a saucepan combine condensed milk brown sugar butter corn syrup and vanilla
Cook over medium low heat stirring constantly
Cook for about 8 to 10 minutes until thickened
Pour the caramel over the cooled crust and spread evenly
Allow to cool completely
Lift the slab out using the parchment or foil
Cut in half and stack the layers gently pressing together
Heat the cream until just simmering
Pour over chocolate chips in a bowl
Stir until smooth
Spread the chocolate evenly over the top
Let cool slightly then sprinkle with flaky salt
Once fully set slice into bars