Season the pork ribs liberally with salt and pepper on all sides.
Place 1 slab on the parchment paper top side down and lay the thinly sliced lemons, garlic & rosemary on the curved side & lay the other slab of ribs on top.
Wrap in the parchment and then wrap in the foil well to seal. Make sure when wrapping that the seam side is on top.
The ribs will cook & steam in their own juices and the whole point of this is to reserve all of the juices for the glaze.
Place rib/foil package on a sheet pan and bake in a 350 degree oven for about 1 1⁄2 hours.
Remove the rib package from the oven and let rest at room temperature for 1 hour before opening, this is very important to insure tenderness and succulence.
Carefully open rib package and remove ribs to another sheet pan and pour all of the juices & fat into a small sauce pot.
Glaze
In a small saucepot, combine the reserved pork juices & fat renderings, add the lemon zest & juice, rosemary & garlic.
In a small bowl make a slurry with the corn starch & water to the consistency of heavy cream.
Bring the pot to a simmer and whisk in the slurry to thicken, the glaze should just coat the back of a spoon, adjust seasonings and add more lemon juice if needed.
To finish: Grill or broil rib slabs and finish with a generous couple of swaths of the glaze, sprinkle liberally with scallions & togarashi.