Mix the flours, salt, yeast, sunflower, caraway, and poppy seeds in a large bowl. Add the black treacle and water, then mix well. If the dough seems a little stiff, add 1 tbsp or more extra water. Mix well, then put on a lightly floured work surface and gently knead the dough for 7 mins. Put it back into a lightly oiled bowl for approx 2 hours until doubled in size.