1. In a large mixing bowl with paddle attachment combine sourdough starter, milk, sugar, eggs, and vanilla. Add flours; mix until combined. Cover and rest 20 minutes. Add salt; knead with dough hook attachment on medium-low 5 minutes. With mixer running, slowly add the 1/2 cup butter, 1 tablespoon at a time. After butter is mixed in, place dough in a lightly greased bowl. Cover and set in a warm place 2 hours (bulk fermentation). During this time, stretch and fold the dough at 30 minute intervals. At the end of bulk fermentation, cover and refrigerate dough at least 2 hours or overnight.

2. Meanwhile, for filling, in a small bowl combine brown sugar; 1/3 cup unsalted butter, softened; cinnamon; cardamom; and nutmeg until a smooth paste forms.

3. Lightly grease a 13x9-inch baking pan; set aside. Turn dough out onto a lightly floured surface. Pat or roll out into a 20x14-inch rectangle. Spread filling over dough, leaving a 1/2-inch border along one long side. Roll up rectangle, starting with the filled long side; pinch dough to seal seam. Slice into 12 equal pieces. Arrange in prepared baking pan. Cover; let rise in a warm place until nearly doubled in size (about 2 hours).

4. Preheat oven to 400°F. Bake 25 to 30 minutes or until golden brown. If using, prepare Caramel Topping during the last 5 minutes of baking. Pour evenly over hot baked rolls. Cool in pan on wire rack. Spread icing over warm rolls.

Caramel Topping

In a small saucepan combine 3/4 cup packed brown sugar, 1/4 cup unsalted butter, and 2 Tbsp. honey. Bring to boiling over medium; cook 1 minute. Stir in 2 Tbsp. heavy cream; remove from heat.

Honey Cream Cheese Icing

In a medium bowl whisk together 4 oz. cream cheese, softened; 2 Tbsp. unsalted butter, softened; 3 Tbsp. honey; 1/2 tsp. ground cardamom; and 1/4 tsp. salt until smooth.