In a large mixing bowl, combine the flour, granulated sugar, and salt. Mix well and set aside.
In a separate small bowl, dissolve the yeast in warm milk. Let it sit for about 5 minutes until it becomes frothy.
Make a well in the center of the dry ingredients and pour in the yeast mixture. Add the eggs and softened butter.
Mix the ingredients together using a wooden spoon or a stand mixer with a dough hook attachment. Continue mixing until a soft and sticky dough forms.
Transfer the dough to a lightly floured surface and knead it for about 5-10 minutes until it becomes smooth and elastic.
Place the dough in a greased bowl, cover it with a clean kitchen towel, and let it rise in a warm place for about 1-2 hours or until it doubles in size.
While the dough is rising, prepare the apple filling. In a small bowl, toss the thinly sliced apples with brown sugar and ground cinnamon until they are well coated.
Once the dough has risen, punch it down to release any air bubbles. Roll out the dough into a rectangular shape, about 1/4 inch thick.
Spread the apple filling evenly over the dough, leaving a small border around the edges.
Starting from one of the longer sides, tightly roll up the dough into a log, making sure to seal the edges.
Using a sharp knife, cut the log into equal-sized slices, about 1 inch thick.
Place the slices in a greased baking dish, leaving some space between each slice to allow for rising.
Cover the baking dish with a clean kitchen towel and let the brioche rise for another 30-45 minutes, or until it doubles in size.
Preheat the oven to 375°F (190°C). Bake the Apple Brioche for 25-30 minutes, or until it turns golden brown and the apples are tender.
Remove the brioche from the oven and let it cool slightly before serving.