Preheat the oven to 375 degrees F. Place the water and spinach in a saucepan. Wilt the spinach, pressing down the spinach with the back of a spoon, about 45 seconds. Drain the spinach, squeezing out the spinach tightly and reserve the liquid. Pour the liquid into a mixing bowl with 4 tablespoons of the butter. The butter will melt and cool the liquid to 110 degrees F. Stir in the yeast and dissolve the yeast. Add the beaten egg, sugar, salt , and black pepper. Finely chop the spinach and add to the yeast mixture. Add the flour and mix well with a wooden spoon until the dough comes away from the sides of the bowl. Using your hands, form the dough into a ball. Lightly oil a bowl. Place the dough in the bowl and turn the dough once. Cover the dough with plastic wrap and place in a warm, draft-free place until the dough doubles in size, about 1 hour. Butter 6 over-sized muffin tins. Invert the dough onto a floured surface and punch it down with your fist. Fold each side in and tuck the ends into the center. Repeat. Put the dough, seam side down and divide the dough into 6 six equal portions. Using your hand, gently roll the dough into a ball. Place the rolls in the prepared pan. Sprinkle the rolls with kosher salt and cheese. Cover and let rise in a warm, draft-free place until in doubles in size, about 1 hour. Bake the rolls for about 30 minutes, or until golden brown. Remove from the oven and place on a wire rack to cool before removing from the pan.