In a large measuring cup or small bowl, combine the yeast and warm water. Stir lightly and let sit for about 5 minutes or until it starts to bubble (proof).
In the bowl of a stand mixer, combine the flour, rye flour, brown sugar, cocoa powder, salt, and caraway seed and stir until well mixed.
Add the proofed yeast mixture, oil, molasses and mustard. Stir well, then attach dough hook and knead for about 5 minutes. The dough will be kind of heavy and might not feel as elastic as some other breads. Transfer it to a large mixing bowl rubbed with a little extra oil. Let rise for one hour or until it's about doubled in size.
Punch down the dough. Divide it into two parts and shape each into a little football shaped loaf. Arrange about 6 inches apart (leave enough room for it to rise) on a large baking sheet. If desired, brush with a little beaten egg and sprinkle on more caraway seeds.
Let rise at room temperature for about 40 minutes.
Preheat the oven to 375 degrees F. Bake in the preheated oven for 38 to 40 minutes or until loaves sound hollow when tapped. Let cool. Slice and serve.