Prepare the Sauce (up to 3 days in advance):

1. In a large heavy-bottomed saute pan set over medium-high heat, sear the duck confit legs in olive oil, skin side down, for 7-10 minutes or until the skin is crisped and brown. Remove from pan and set aside to cool.
2. Add garlic and shallots to the pan, and saute for 10 minutes, or until soft and lightly coloured. Reduce the heat to low and continue cooking, stirring occasionally to prevent burning, for 10 minutes or until the shallots are lightly caramelized.
3. Deglaze the pan with sherry and balsamic vinegar, scraping up any browned bits clinging to the bottom. Return the heat to medium-high, and simmer for 3-5 minutes or until liquid is reduced by about half.
4. Stir in the stock and thyme, and continue simmering for 10-15 minutes or until reduced to 1 1/2 cups of liquid.
5. Pour the jus through a fine-mesh strainer into a bowl. Discard the solids.
6. Add butter to the pan, and heat until foamy. Add flour and cook for 2 minutes, stirring constantly. Slowly whisk the jus back into saucepan, and cook until thickened and smooth, about 5 minutes. Remove from heat.
7. Pull the meat off the cooled duck legs, and coarsely shred, discarding any gristle and fatty bits. Stir into the warm sauce.
8. Finished sauce will keep for up to 4 days in the refrigerator - simply reheat over low heat when ready to serve. (If using right away, keep the sauce warm over very low heat while you cook the fries)

Prepare the French Fries:

1. Start on the fries by cutting the potatoes lengthwise into 1/4" slices, then cutting the slices into 1/4" sticks. Transfer to a large bowl of ice water to soak for at least one hour, or up to 8 hours.
2. About 15 minutes before serving time, pour oil into the deep-fryer up to the "maximum" fill line (or roughly halfway up the sides), and heat to 325F.
3. Using paper towels, pat the potatoes completely dry (be as thorough as possible - wet potatoes plus hot oil equals spatter!). Working in small batches, fry the potatoes for 3-4 minutes, or until lightly browned and still very soft. Remove from oil and transfer to a baking sheet lined with paper towel to drain.
4. Increase the oil temperature to 375F. Still working in batches, return the fries to the fryer for 3-4 minutes longer, or until crispy and golden brown. Remove and set on a fresh layer of paper towels to drain. Sprinkle the fries generously with salt as they come out of the fryer.

Assemble the Poutines:

1. To serve, divide the hot fries between 12 small serving bowls. Top each poutine with a few crumbles of cheddar cheese, a generous spoonful of shredded duck and jus, and finish with a sprinkling of chopped thyme. Serve immediately.