In a large bowl, combine the rye flour, all-purpose flour, sugar, salt, and cocoa powder (for the darker marble section). Whisk them together to make sure they’re evenly mixed. This will give you a solid foundation for your dough.

In a separate bowl, combine the warm water with the active dry yeast. Stir it gently and let it sit for about 5-10 minutes until it becomes frothy. This means the yeast is activated and ready to do its magic. If the yeast doesn’t foam, it may be expired, so try again with a fresh packet.

Once your yeast mixture is bubbly, pour it into the dry ingredients. Add the olive oil and mix everything together with a spoon or your hands. You’ll start to see the dough form, and at this point, you can switch to kneading. If the dough feels too sticky, add a little extra all-purpose flour—just be careful not to add too much, as you want it to stay soft and manageable.

Turn your dough out onto a floured surface and knead it for about 8-10 minutes. The goal here is to develop the gluten, which gives the bread its structure. Don’t rush this process—kneading helps create a light, airy texture. Once the dough reaches a smooth and elastic consistency, form it into a round shape.

Transfer the dough to a bowl coated with a thin layer of oil, then cover it with a damp cloth. Allow the dough to rest in a warm spot for 1-2 hours, or until it has doubled in size. If you’re having trouble finding a warm spot, you can preheat your oven to 200°F (93°C) for a few minutes, turn it off, and place the bowl inside for the dough to rise.

Once your dough has risen, gently press it down to expel any air pockets. Now, split the dough into two equal portions. Keep one portion as-is for the light rye dough, and mix cocoa powder into the second portion for the dark rye dough. Knead the cocoa powder into the dark dough until it’s evenly incorporated, creating a rich, chocolatey color.

Here’s where the magic happens! Take both portions of dough and roll each into a log, ensuring they're roughly the same length. Stack the logs on top of each other, then gently twist them together to create that signature marble effect. Be careful not to overwork the dough—just enough to get a beautiful swirl.

Place the twisted dough into a greased loaf pan, cover it with a cloth, and let it rise for another 45 minutes to 1 hour. This will allow the dough to puff up and take on its final shape.

Preheat your oven to 375°F (190°C). Once the dough has risen, place it in the oven and bake for 30-35 minutes, or until the top is golden brown and the loaf sounds hollow when tapped on the bottom. You can also check the internal temperature with a kitchen thermometer—aim for about 190°F (88°C) inside the loaf.

Let the marble rye bread cool on a wire rack for at least 30 minutes before slicing. This allows the flavors to set and ensures the loaf maintains its shape. Once cooled, slice and enjoy!