Let all wet ingredients (butter, eggs, and milk) come to room temperature
Place spelt flour, salt, sugar, and yeast in the bowl of the stand mixer with the dough hook attached. Be sure that the salt and yeast are on opposite sides of the bowl.
Turn the mixer on slow to start combining dry ingredients
Add butter in chunks to the dry ingredients and allow to incorporate a little. Keep the butter wrapper for later use.
Add beaten egg and then add milk a little at a time until all is incorporated
Mix on low for 4 minutes then increase to medium-low for an additional 6 minutes
Turn out on a dry counter and hand-knead approximately 30 seconds or until smooth and satiny
Use the butter wrapper to lightly grease the large mixing bowl
Place the dough into the greased mixing bowl and cover with plastic wrap. Allow to rise in a warm place for 30-60 minutes. The dough may not double in size but should increase somewhat.
Use the butter wrapper to lightly grease the 9x13 baking dish
Turn out onto a dry counter and lightly flatten
Weigh the dough and divide into 15 even pieces by weight
Roll into ball shapes and place evenly in baking dish (3x5 rolls)
Cover with a tea towel and allow to proof 30-45 minutes
Preheat oven to 480F / 250C
Beat egg and water together to form an egg wash and brush over the tops of the rolls
Bake 10 minutes