Slice the butternut sqash in half, remove seeds and drizzle over some olive oil. Roast for 45 -60 minutes or until the butternut squash flesh is soft enough to scape out of the skins and mash or puree. Set aside to cool.
In a mixing bowl, dissolve yeast in water; let stand for 5 minutes.
Add mashed or pureed butternut squash, milk, beaten eggs, butter, brown sugar and salt; mix well. Gradually add plain flour about 100g at a time; mixing until smooth. Add more flour to form a dough. Turn onto a clean, floured surface; knead until smooth, about 5 minutes. Place in a glass bowl, lightly gresed with vegetable oil and roll around to lightly coat the dough. Cover with a clean te towel and let rise in a warm place until doubled in size, about 1 hour.
Divide the dough and make into three loaves; place each one in a greased 1 pound loaf tins. Cover and let rise in a warm place until doubled, about 30 minutes.
Preheat the oven to 200 degrees C.
Bake for 25-30 minutes or until tops are golden. Remove from pans to cool on wire racks.