Much, Much Better Focaccia

I tried again, this time with inspiration from Cook's Illustrated. I should have known this was the way to go.

Dough
1 medium baking potato, peeled and quartered
1.5 t instant yeast
3.5 cups AP flower (17.5 ounces if you're into weighing)
1 cup warm water (110 degrees), divided
2 T olive oil, plus more for oiling bowl and pan
1.25 t kosher salt

Topping
2 T olive oil
2 T fresh rosemary leaves
coarse sea salt

Dough: Boil potato in water for about 25 minutes, or until done. Drain, let cool and pass potato through ricer or grate on large holes of a grater. You need 1.3 cups, lightly packed.

Meanwhile, mix the yeast, 1/2 cup of flour and 1/2 cup of warm (110º) water in large bowl of mixer until combined. Cover with plastic wrap and let sit for about 10 minutes, or until bubbly. Then add remaining dough ingredients, including the reserved potato. Attach the paddle and mix just until combined, then use the dough hook on it for 5 minutes at medium speed.

Transfer to lightly oiled bowl, cover with plastic wrap and let rise for an hour.

Then transfer to well oiled large sheet pan, using your fingers to spread it all out. Wet your hands, or cover them with oil, to make this easier. Cover with plastic wrap (the dough, not your fingers) and let rise for another hour.

Preheat oven to 425º and make sure rack is toward middle bottom of the oven – not exactly on the bottom, or the crust will burn. With two wet fingers, make dimples down the dough – think of it like a big football field, and you're marking out the yard lines every 10 yards or so ... Add the topping and bake for 25 minutes. Cool immediately on a wire rack, or the bottom crust will get soggy.

Just try not to eat it piping hot. Just try.