Mix the ingredients. Add all ingredients to the bowl of an electric stand mixer or a large mixing bowl. Combine until a dough forms that holds together and does not stick to the sides or bottom of the bowl. As the butter melts and is worked into the dough during kneading, it will make the dough more hydrated, so hold off on adding any more water now, even if it seems a bit dry.
Knead the dough. Knead for ten to fifteen minutes until it is smooth, soft, and reaches the windowpane stage (meaning that when the dough is stretched, a translucent area appears). If the dough is still dry after a minute or two of kneading, sprinkle on the water a teaspoon at a time. Different brands of whole wheat flour can absorb moisture differently, so you may need to adjust a little.
The first rise. Shape the dough gently into a ball and place it into a clean, lightly oiled bowl. Cover with a clean, damp tea towel and place into a warm place to rise. Let the dough rise for 60 minutes until it is puffy and has doubled in size.
Shape into a loaf. Spray the loaf pan with nonstick cooking spray. Gently stretch the dough into a rectangle. Use your loaf pan as your guide and make the short side of the rectangle the same length as the longer side of the loaf pan. The rectangle will be about 9 x 18 inches. Tuck in the corners and top of the dough. Think of the saying "shoulders in, head down." Keep rolling into a log. Tuck the ends under. Pinch the seams closed and place the loaf, seam side down, into a lightly oiled loaf pan.
Second rise. Cover with heavily greased plastic wrap and place in a warm place to rise again until the dough rises to one inch above the top of the loaf pan. The bread will rise very slightly as it bakes, so make sure you are happy with the height of the bread before you bake it. Towards the end of the rising time, preheat your oven to 350 degrees.
Bake. Bake at 350 for 45-50 minutes, until the loaf sounds hollow when tapped. If you have an instant-read thermometer, check the temperature. Whole wheat loaves can be difficult to eyeball since they are darker, to begin with. The finished bread should be between 195-200 degrees. Remove the bread from the loaf pan and allow it to cool fully on a wire rack. Wait to slice until the loaf is fully cooled.