Line two baking sheets with baking parchment. Temper the plain, milk and white chocolate. Chop the mini eggs.
Pour half of the melted white chocolate in a line down the middle of the baking sheet. Repeat on the second baking sheet with the remaining white chocolate.
Now pour lines of plain chocolate down one side of the white chocolate and milk chocolate on the other side.
Gently tap the baking tray on the work surface so that the chocolate spreads and slightly flattens.
Using the blade of a dinner knife swirl the white chocolate into and out of the chocolate either side. You can also tease the sides of the chocolate out so that it forms a rough rectangle.
Sprinkle the chocolate with chopped mini eggs or a little bit of finely chopped fresh rosemary and seasalt crystals to complete. Allow to set before breaking into chunks to serve,