Chop the rosemary up as fine as you can get it, then place to one side.
Sift the flour and sugar into a medium sized mixing bowl.
Cut the butter up into small flakes add it to the bowl and using your finger tips gently rub it into the flour until it resembles very fine breadcrumbs.
Stir in the fresh rosemary and smoked sea salt.
Add in the cream and 3 tablespoons of water.
Using a round bladed knife, mix everything together. Add more water if needed, one teaspoon at a time to make a soft but not sticky dough. It will feel a little like a short crust pastry.
Lightly dust your work surface with a little flour, knead your dough for just 5 seconds to smooth it out a little but no longer.
Place the dough back into the bowl and cover with clingfilm (plastic wrap) and leave to relax the dough for 30 minutes.
Near the end of the 30 minutes, preheat your oven to 180C / 350F / Gas mark 4. And line 2 medium baking sheets with baking parchment.
Lightly dust your worktop again with flour, then roll out the dough to a very thin sheet approx. 35cm x 45cm.
Cut the sheet in half and very gently lift one half onto your lined baking sheet. Prick the dough all over with a fork and using a very sharp knife or a pizza cutter trim the edges off so they are nice and neat. Then cut the dough into equal squares. Repeat the process with the other sheet of dough, if you only have one baking sheet do this in two batches.
Then place the dough into your hot oven and bake for 15 - 17 minutes until they are a lovely light golden colour. For a slightly more even bake, rotate the baking sheet half way through baking.
Remove them from the oven, don't panic its perfectly natural that they have shrunk during baking, allow them to sit on the hot tray for 2 minutes.
Transfer the crackers to a wire rack to fully cool down.
If you keep them in an airtight tin at room temperature they will keep for up to 5 days.