Line a 13" x 9" cake pan with parchment paper leaving enough on the edges so that the chelsea buns can be lifted out easily on the paper. If you don't line the pan, the buns will likely stick to the pan.
While the dough is rising peel and dice the apples.
Melt 2 tbsp of butter in a frying pan and sautee the 3 cups of apples for 10 to 15 minutes to soften them and get rid of the excess juice. When the apples start to take on a little colour then they are done. Put them in a bowl until you are ready to spread on the rolled out dough.
When the dough has proofed for 1 1/2 hours, roll the dough out onto a floured board using a rolling pin so that it is 14" x 18".
Melt the remaining 2 tbsp of butter and spread it over the dough, leaving a 1" perimeter around the edge.
Mix the brown sugar and cinnamon together and sprinkle it evenly over the buttered dough.
Spread the cooked apples over the cinnamon and brown sugar as evenly as you can.
Starting with the long side closest to you, begin rolling the dough away from you. Use your fingers to make sure the dough stays tight and even as you roll it.
With the seam on the board, cut the log into 3 even pieces using a serrated knife. Then cut each third into 4 even pieces.
Holding the seam of each piece, put each piece evenly spaced on the parchment paper on the pan. For the two end pieces, place them cut side down in the pan.
Cover the pan with plastic wrap and let it rise for a second time for 45 minutes.
Preheat the oven to 350 F
Remove the plastic wrap after 45 minutes and bake for 30-33 minutes.
While still hot from the oven, spread as much dulce de leche or your favourite caramel sauce on top of each bun. About 3/4 cup will give each bun a generous amount but you can always use more.