Put the raisins in a small bowl and cover them with a cup of hot water. Let the raisins plump for at least 10 minutes. Drain and toss with a few tablespoons of flour to absorb any residual moisture.
In the bowl of a stand mixer, add 1/3 cup warm water, a teaspoon of brown sugar and then sprinkle the yeast over top. Give it 4-5 minutes to foam and bubble, then stir to fully dissolve the yeast into the warm water.
Add the warm milk, rolled oats, brown sugar, cinnamon, sea salt, softened butter and bread flour to the bowl and mix on low for 1 minute. Add the raisins to the bowl. Knead the dough in your mixer on low speed with a dough hook for 8-10 minutes to form a smooth, slightly tacky dough. Check the dough halfway through; if it’s very sticky, add a little more flour.
Pour the dough in a greased bowl and cover with a clean towel or plastic wrap. Let the dough rise in a warm place until doubled in size, about an hour.
When the dough has finished rising, shape it into a rectangle, and place it in a lightly greased 8 1/2" x 4 1/2" loaf pan. Let the dough rise until it's mounded and looks pillowy, about 1 more hour. Towards the end of the rising time, preheat the oven to 350°F.
In a small bowl, whisk the egg and 1 tablespoon cold water together. Brush the top with egg wash. Bake for 40-45 minutes until golden brown. If the top of the bread is browning too quickly, place a piece of tin foil over the top for the remainder of the bake time.
Remove from the oven and let cool in the pan for 5 minutes. Remove the loaf from the pan and allow to cool completely before slicing. Baked loaves can also be frozen for up to three months in an airtight container.
