Peel the potatoes and cut into chunks. Add to a large pot of water and place over high heat. Bring the water to a boil and cook until the potatoes are fork tender. Meanwhile, combine the heavy cream, ⅓ cup of the ale, and 4 tablespoon of the butter in a small saucepan and place over low heat. Allow the cream mixture to warm until the butter melts. Keep warm until the potatoes are done.
In a medium saucepan, add the olive oil and place over medium heat. Add the shallots and sauté for 4 to 5 minutes until the shallots are softened and golden brown. Add the remaining ale, turn up the heat and bring to a boil. Allow the ale to simmer until it reduces to about a half cup of liquid.
Once the ale has reduced, add the honey, grainy mustard, malt vinegar, Worcestershire sauce, ½ teaspoon of the kosher salt, and pepper. Continue simmering for another 3 to 4 minutes to allow the mixture to reduce a little more. When the mixture begins to look a bit syrupy, whisk in the remaining tablespoon of butter.
In a small cup combine the cornstarch with 1 teaspoon of water to make a slurry. Whisk the slurry into the reduction and cook for another minute. Allow the mixture to boil and thicken before removing from the heat. Taste the reduction, adding a bit more honey if needed.
When tender, drain the potatoes and transfer back to the pot. Use a potato masher to break up the potatoes into a rough mash. Slowly add the warm cream mixture in two or three batches, mashing into the potatoes between additions. Depending on how soft the potatoes are, you may not need all of the liquid.
Once the liquid has been added, season the mash with the remaining teaspoon of kosher salt. Add the shredded cheddar cheese and fold in with a spatula. The heat from the potatoes will melt the cheese. Keep warm.
To serve, spoon half of the potatoes into a large serving bowl. Drizzle with half of the ale reduction and sprinkle with some of the chopped chives. Spoon the remaining mashed potatoes into the serving bowl and finish with the remaining ale reduction and chopped chives. Enjoy!