Rinse the French roast and pat dry. Season well with salt, pepper, and paprika.
Place the sugar in a sauté or braising pot (the pot should also be large enough to fit the meat, covered). Over low heat, cook sugar, stirring occasionally, until sugar melts and turns into a caramel color.
Add the meat to the pan on top of the caramelized sugar. Sear both sides of the meat two times, using a fork or tongs to rotate the meat.
When all surfaces of the meat are browned, lift the roast and place the onions underneath. Cover and let cook over medium low heat for 21/2‑ 3 hours. (Make sure the flame is low enough so as not to burn the meat, but high enough so that the sauce is still bubbling slightly.) Remove meat from pan.
As the onions cook, the water from the onions will mix with the sugar, creating a sauce.
In a small bowl, combine the potato starch and water. Add to the sauce. Cook until the sauce thickens. Slice meat and serve with caramelized onion sauce.
Notes
To freeze and rewarm: slightly undercook the roast. Freeze the meat and sugar-onion sauce separately. Rewarm the sauce, only adding the potato starch and water at this point. Slice the meat and reheat with the sauce.I’ve skipped the potato starch many times. Just slice cold meat, pour over the onions and sauce and reheat, or freeze and reheat as needed.