In the bowl of a stand mixer, whisk warm milk, sugar and yeast. Cover and leave to rest for 10 minutes.
Add the melted butter and egg and whisk till combined.
Add in the flour and salt and mix till dough starts to form. Change to the dough hook and knead for 2 minutes. Dough will be a bit sticky.
Transfer dough to the instant pot. Close the lid and put the setting on yogurt mode. Leave to rise for 20 minutes or until double in size (if not using the instant pot, transfer dough to a large well-oiled bowl, cover with a damp towel and leave in a warm place to rise for 1 hour or until double in size).
Preheat oven to 350°F and line a 9-inch square baking tray with parchment paper.
Remove dough from Instant pot, roll out on a lightly flour surface to a 9x13 inch rectangle. Spread the butter evenly over the dough, leaving ¼ inch border all around.
Sprinkle the brown sugar and cinnamon over the buttered dough, and press them into the butter lightly with your fingers. Sprinkle the white chocolate pieces.
Starting with the long side, roll up the dough to a log and pinch the seams together.
Slice the dough with a sharp knife or floss into 1-1½ inch cuts. Trim off the edges on either side which will not have enough filling.
Put the slices on the baking tray, evenly spaced. Leave to rise in a warm place for another 30 minutes.
Bake at 350°F for 25 minutes, or until lightly golden brown. Cool on a wire rack for 5 minutes.