In a small bowl stir together the lukewarm milk and 1 tablespoon of sugar, sprinkle the yeast on top and let sit for approximately 10 minutes. Stir to combine.
In the bowl of the stand mixer whisk together the flours and salt, add the yeast mixture and start to knead with the dough hook on low speed, add the butter and continue to knead on speed #2 for approximately 6-8 minutes or until elastic and dough pulls away from the sides of the bowl. The dough should be soft, if needed add a bit more butter.
Move the dough to a lightly floured flat surface, shape into a ball, place in a lightly oil bowl, turning to cover the ball of dough. Cover with plastic wrap and place in a warm draft free area to rise until doubled, approximately 2 hours.
Gently remove the dough to a lightly floured flat surface, knead a few times and form the dough again into a ball.
Grease a 9 inch square pan with 2 tablespoons of the softened butter, it should be well buttered, sprinkle with 2-3 tablespoons of granulated sugar, place the dough ball on top and let sit covered with a clean kitchen towel for 10-15 minutes.
Gently stretch the dough with your hands to fit the pan. Cover with the towel and let rise in warm draft free area for 1 hour.
Pre-heat oven to 350F (180C).
Make dents in the dough with your fingers, brush the dough with the melted butter and sprinkle with 2-3 tablespoons of granulated sugar.
Bake for approximately 25-30 minutes or until golden and baked. Move immediately to a rack. Serve warm. Enjoy!
Notes
The dough can be made by hand, be sure to knead for approximately 15 minutes.To make homemade pastry flour, for every cup of all purpose flour remove 2 tablespoons of flour and replace with 2 tablespoons of corn starch, sift together to remove any lumps.Sweet focaccia is best fresh, but if you have leftovers you can store it at room temperature for 2-3 days. Store it in plastic wrap or in an airtight container.