Mix milk, yeast, sourdough, salt, honey, and whole wheat flour together in a mixing bowl to avoid lumps. Personally, I use a stand mixer and run it for 3-5 minutes at speed 2-3.

Add the flour gradually at speed 3-4 and mix until the dough pulls away from the bowl, which takes 7-10 minutes. I use a paddle attachment, but a dough hook can also be used.

Let the dough rise for an hour under a shower cap or plastic wrap at room temperature.

Grease a sandwich bread form with butter and set aside.

Turn the dough out onto a floured surface and knead well for 3-5 minutes. Roll the dough into a tight loaf and divide it into 4 equal pieces.

Place the dough in the greased bread form. Rotate each piece of dough 90 degrees, and place the dough closely together. Put the lid on the sandwich form and let the bread rise for 4-7 hours until the dough reaches the top of the form. If you don't have a sandwich form, use a regular bread form and use an ovenproof dish as a lid. Remember to grease the bottom of the dish so the bread can easily come out when baked.

By using this technique of dividing the dough into 4 pieces and rotating each piece 90 degrees, you achieve the same texture as a good toast bread, where it's easy to spread without breaking the bread.

Preheat the oven to 250 degrees Celsius (482 degrees Fahrenheit) (fan), and let the baking tray get hot in the oven.

Bake the sandwich bread for 10 minutes at 250 degrees Celsius (482 degrees Fahrenheit) (fan), then reduce to 210 degrees Celsius (410 degrees Fahrenheit) (fan) and bake for another 20 minutes. By baking the bread at high temperatures, you ensure a deliciously hard crust.

Turn the bread out onto a wire rack as soon as it is done baking. Let the bread cool on the wire rack.