For the dough, heat milk in a microwave-safe measuring cup for 45 seconds to 1 minute, until very warm (120-130°F). Combine warm milk, yeast, salt and honey in a large mixer bowl; mix on low speed until incorporated. Add eggs and melted butter; mix until combined. Gradually mix in flour, just until combined. Cover mixer bowl loosely with plastic and let rest in a warm place for 45 minutes.
After 45 minutes, the dough will be puffy and doubled in size. Transfer dough to the refrigerator and chill for 2 hours.
Remove chilled dough from the refrigerator. Gently press down dough; cover and let rest for 5 minutes. Spray a 13x9-inch baking pan with nonstick spray.
Turn dough out on a lightly floured board, dust with dough lightly with flour, and roll into an 18x12-inch rectangle. Spread dough with softened butter, leaving a ¼-inch border. Combine brown sugar, cinnamon, and salt; sprinkle over dough and press gently into dough with rolling pin. Carefully roll dough up into a tight log and pinch edges to seal (if dough starts to stick, use a bench scraper to lift dough from the board).
Trim off uneven ends and score dough into 12 equal slices. Use unflavored dental floss to slice dough crosswise (slip a long slice of floss under log of dough and cross on top to cut slices cleanly). Place rolls cut side up into prepared baking pan and cover tightly with plastic. Let rest in the refrigerator overnight (up to 16 hours).
On baking day, remove the chilled rolls from the refrigerator and place in a warm spot to rise until puffy (about 45 to 60 minutes) before baking.
While the rolls rise, preheat the oven to 350°F and make the frosting: Combine butter, salt, powdered sugar, milk and vanilla bean seeds in a large mixer bowl and beat until smooth and creamy.
Bake rolls for 28 to 32 minutes, or until golden. Remove from oven and place on a wire rack to cool for 20 minutes. Spread the frosting over the warm rolls before serving.