In a mixing bowl, combine warm milk and active dry yeast. Let it sit for about 5-10 minutes until foamy.
In a stand mixer bowl, mix together the flour, sugar, and salt. Gradually add the yeast mixture and eggs to the dry ingredients.
Using the dough hook attachment, knead the dough on medium speed for about 5 minutes.
Slowly incorporate the softened butter, a few cubes at a time, and continue kneading for another 10 minutes until the dough is smooth and elastic.
Transfer the dough to a greased bowl, cover with plastic wrap, and let it rise in a warm place for about 1-2 hours, or until doubled in size.
Once risen, punch down the dough and turn it out onto a floured surface. Roll it out into a rectangle about ½ inch thick.
Spread the raspberry preserves evenly over the dough. If using fresh raspberries, gently mash them and spread them as well.
Starting from one long edge, roll the dough tightly into a log. Pinch the seams to seal.
Twist the dough log into a spiral and shape it into a loaf. Place it in a greased loaf pan.
Cover the loaf with plastic wrap and let it rise again for 30-45 minutes until puffy.
Preheat the oven to 350°F (175°C).
Once risen, bake the loaf for 25-30 minutes, or until golden brown and a toothpick comes out clean.
Remove from the oven and let it cool in the pan for about 10 minutes before transferring to a wire rack.
Slice and serve the delicious Raspberry Swirl Brioche Loaf!