For the dough: Combine the milk and 6 tablespoons of the butter in a pot. Stir in the sugar. Scald the milk mixture slightly by heating it almost to a boil. Turn off the heat and let cool until just warm to the touch, about 10 minutes.
Add the flour, yeast, baking soda and salt to the milk mixture in the pot and stir until well combined. Cover the pot with a dish towel and place in a warm spot in the kitchen. Let the dough rise for an hour or so. It should roughly double in size.
Divide the dough into 12 equal parts and roll each into a neat ball. Place the balls on a baking sheet sprayed with cooking spray. Cover with a dish towel and set aside in a warm place to rise for another 20 minutes.
For the water bath: While the dough is rising, bring a pot with 10 cups of water to a boil. Stir in the baking soda.
Preheat the oven to 425 degrees F. Melt the remaining 2 tablespoons butter in a small pot or in the microwave.
Working in 3 batches of 4 rolls each, drop the dough balls into the water and boil for 30 seconds. Transfer the boiled balls to a baking sheet lined with paper towels to drain.
To bake the rolls: Transfer the rolls to a parchment-lined baking sheet. Using a sharp knife, make a small "x" in the top of each roll. Brush the tops with the melted butter and sprinkle with sea salt. Bake until deep brown, about 15 minutes.