In a large bowl, whisk together the flour, cocoa powder, and salt. Add the starter, water, honey, and vanilla. Mix to combine and form a rough dough. Let rest for 45 minutes to 1 hour.
Add the chocolate chips and gently knead to incorporate. Cover and let rise overnight at room temperature for 12–18 hours.
Preheat the oven to 425°F (220°C). Melt butter and coat a 10-inch cast iron skillet with it. Transfer the dough to the skillet and flip to coat both sides with butter. Let rise for 1 hour.
Dimple and stretch the dough to fit the skillet, sprinkle with extra chocolate chips. Bake for 35–40 minutes, until golden brown.
Cool for 10 minutes. Spread Nutella over the top and dollop with cream cheese. Add fruit and dust with powdered sugar. Serve warm.