Slice bacon into about 1/2" strips. Place bacon in a large skillet over medium to medium high heat. Cook until crispy. Turn off heat and remove bacon from skillet with a slotted spoon and place on paper towels. Leave bacon grease in the pan.
In a small bowl combine salt, pepper and Herb De Provence. Set aside.
Preheat oven to 400 degrees F.
Cut off the bottom ends of the Brussels sprouts and discard. Cut them in half and place into a large bowl. Drizzle with 2 tablespoons olive oil and half of the salt, pepper and Herb De Provence mixture; give it a good mix. Spread this mixture in a baking sheet in one layer.
Place the baking sheet into the oven and roast for 40 minutes. Remove the baking sheet every 15 minutes while roasting and give the Brussels sprouts a good toss to make sure they are evenly roasting and browning.
10 minutes before they are done, squeeze an entire lemon or lime on top of the vegetables and place back into the oven to finish roasting. Once the edges are crisp and brown, remove the baking sheet from the oven.
While the Brussels sprouts are roasting, scrub potatoes and stab all over with a fork. Place on a paper towel lined plate and microwave on high until pierced easily with a knife.
Cool a bit, peel off skins and cut into 1/2" large slices. Place them in a very large mixing bowl and toss them with the remaining 1 tablespoon of oil, 2 tablespoons of apple cider vinegar and salt, pepper and Herb De Provence mixture. Set aside and make the Ale dressing.
For the Ale dressing
To make the dressing; Heat the skillet with the bacon grease and 1 tablespoon of oil over medium-high heat. Add onion and sauté until onions are translucent, about 5 minutes. Add a pinch of salt and pepper, ale, vinegar and sugar. Cook until liquid is reduced by a third, about 5 minutes.
Transfer onion and ale mixture to food processor. Add mustard and garlic; blend until smooth. With machine running; drizzle remaining oil through feed tube to form smooth dressing. Season dressing to taste with salt and pepper.
To serve; add the hot roasted Brussels sprouts, bacon, green onions and parsley to the bowl with the potatoes; add the warm dressing and toss well to combine. Taste salad and season, if needed, with some more salt and pepper, sprinkle shredded Cheddar cheese on top and serve warm.