Two most common reasons: Using the wrong type of flour. You need an extra strong bread flour which has a higher protein content and therefore more gluten. As a result, the dough holds together well but is also very elastic. Perfect for making soft and fluffy hot cross buns. Under kneading. For extra strong bread flour to give soft and fluffy hot cross buns you must knead your dough. Knead the dough until it is smooth and elastic. Not sufficiently working the dough and stretching the gluten is likely to deliver a dense or tough hot cross bun.