In the stainless steel bowl of your stand mixer, add whole wheat flour, bread flour, salt, sugar, egg and instant yeast.
Add olive oil and turn on the stand mixture at speed 1 or 2 with flat beater attachment.
Add warm water into the mixture till the dough starts coming together.
Replace the flat beater with dough hook once the dough comes together and knead for 7-8 minutes at slow speed [1 or 2]. In case you are kneading with your hands, knead for around 15 minutes till the dough looks smooth. It will be sticky.
Once the dough appears smooth, apply some oil on top and place it in a bowl. Keep the bowl in a warm place for 1-1.5 hours.
The dough will double in size after 1.5 hours, take it out and punch it down to flatten it. Knead with hands or in the stand mixer for a minute or two.
Shape the bread loaf and put in the loaf pan.
Apply some oil on top and keep it in a warm place for 20 minutes again. Preheat the oven to 375 F.
The dough will rise for a second time after 20 minutes or so.
Place the pan in the oven and bake at 375 F for 35-40 minutes.
When done, the bread will appear golden brown and sound hollow when tapped from bottom.
Let the bread cool completely before cutting it into slices. Apply some butter or oil on top.