Preheat your oven to 325
Remove 1.5 cups of sourdough discard from your sourdough starter and add to a separate bowl.
Melt butter and then let it cool for about 10- 15 minutes before adding it to the sourdough starter. You want to make sure it hasn't re-hardened but if it's too warm, your crackers will turn out like crisps (which are delicious in soups and salads) instead of crackers.
Once the butter is added add the table salt, parmesan and mix everything thoroughly. You want to make sure the butter is totally combined with the starter dough. You shouldn't be able to see any hint on it on the surface or on the sides.
Add parchment paper to a cookie sheet and then pour your mixture onto it. Use a spatula and spread out the cracker mixture. You want the dough about 1/8 of an inch thick.
Add them to the oven for 30 minutes.
After 30 minutes remove them from the oven. Cut the cracker shapes with a pizza cutter or a pasta cutter. Or, you leave them whole and just break them later.
Add your sea salt by sprinkling it over the crackers.
Put them back int he oven for another 30 minutes.
Remove and let cool. Keep in an airtight container to keep them fresh.