In a large mixing bowl, stir together 330 grams of water and 100 grams of active sourdough starter. Mix until fully incorporated.
Stir in whole wheat and bread flour. I usually start out by mixing with a spoon and then switch to my hands, because it's easier to incorporate together. Mix until everything is well combined, dough is sticky and shaggy, and there are no white floury bits left.
Cover the bowl with saran wrap and let it rest on the counter for 1 hour, allowing the water to hydrate the flour.
Add the remaining 30 grams of warm water to a small bowl and mix in the 10 grams of salt until fully dissolved. Add this mixture into the dough and use your hands to fully incorporate the salt water into the dough.
Cover bowl with saran wrap and let the dough sit on the counter for 1 hour.
Perform three sets of stretch and folds over the next 1.5 hours, spaced 30 minutes apart. Right before you do your second round of stretch and folds, add in your sun dried tomatoes and parmesan pieces. Stretch and fold these into the dough over the next two sets (you don't need to do any additional mixing, they will get well incorporated throughout the process).
After you have completed three sets of stretch and folds, cover the bowl with saran wrap and let the dough rise on the counter for 2-3 hours.
After the dough has risen for 2-3 hours and noticeably increased in size, place onto a floured surface to shape. I like to stretch the dough into as flat as a 'sheet' as I can make it, and then fold like a tri-fold piece of paper. Then roll it up into a ball and create surface tension by turning the dough ball and dragging it towards you a couple times.
Place dough in a floured proving basket or small bowl lined with a floured tea towel. Wrap in saran wrap and store in fridge between 8 to 36 hours.