Pre-heat your oven to 160C Fan/350F/Gas Mark 4 and grease and line a 12" x 9" traybake tin (check the recipe notes if you want to make in a 8" or 9" square tin)
Melt the dark chocolate and butter together in a pan on a low heat. When fully melted, stir together and remove from the heat. Let it cool for 10 minutes
In a bowl whisk together the eggs and light brown sugar for 5 minutes using an electric mixer until frothy
Add the chocolate mixture to the egg mixture, whisking constantly as you pour it in
Add the plain flour and vanilla extract. Whisk in until you can't see anymore flour
Pour the batter into the lined tin, add small blobs of salted caramel sauce all over, swirl them into the batter gently with a butter knife
Bake for 15 minutes. While it is baking, cut the Caramel Eggs in half and sprinkle coarse sea salt over them. There will be one extra half - the perfect snack for the chef!
Take the brownies out of the oven, press the eggs into the batter, then put them back in the oven for 5-10 minutes. To check if they are done, insert a toothpick in the centre. It should come out with several crumbs on, but not be wet.
Let the brownies cool completely in the tin before removing and slicing up (this is important to make sure the brownies set!) some people like to chill them in the fridge before slicing too, so feel free to do this if you like your brownies this way
Store in an airtight container in a cool place and eat within 3 days