First we will begin making the dough. Heat up milk in a small sauce pan until it begins to simmer. Remove from heat and add salt and stir. Let it cool down to lukewarm to the touch.
Once milk is cool, add to a large bowl fitted for stand mixer, along with flour, oil, egg, pumpkin puree, spices, sugar, and instant yeast. Attach dough hook to the mixer and mix on low until dough forms, about 2 minutes. Once dough is formed, increase speed to medium low and knead for 5 minutes until dough is smooth.
Lightly grease another large bowl and place the ball of dough into bowl. Cover with a kitchen towel and let it rise for 1 ½ hours, where it will be double the size. I like to place mine in the microwave to keep it away from any cool draft from the A/C.
When dough has finished rising, remove cover and, using your fist, punch the dough down and remove from the bowl. Roll out on a well-floured surface into a 12x20 inch rectangle and spread 1.5 tablespoons of softened butter to the edges. Mix the brown sugar with the remaining cinnamon and nutmeg and sprinkle evenly across the butter.
Cut rectangle into 5 even strips vertically. Then, cut each strip into 4 squares. Stack all the squares together (don't smoosh them down tightly) and place into greased 9x5 loaf pan. If any filling spills onto the counter, simply scoop it up and sprinkle over the loaf in the pan. Cover again and let rise for another 30 minutes. Preheat oven to 375 degrees.
Once the loaf has risen, bake in the preheated oven for 25-30 minutes or until the tops have turned golden brown and the center reaches 205 degrees. Remove from oven and let cool for 10 mins while you make the icing. The, remove and place onto serving plate. If you leave it in the loaf pan, it will be hard to get out once completely cooled.