Place a medium-sized skillet over medium heat. Add butter. Once melted add shallots to the and stir. Cook until shallots become translucent, about 4 to 5 minutes.
Add whiskey and stir. Continue cooking, stirring occasionally, until shallots absorb the whiskey. Reduce heat to medium-low and cook for another 10 to 15 minutes until shallots become soft and caramelized.
When the shallots are almost done, cut each meatloaf slice in half to create squares. Cook meatloaf in a large skillet over medium heat flipping once. Once the meatloaf is warmed through and seared on the outside, about 3 minutes per side. remove from heat.
Whisk together mayo, ketchup, brown sugar and mustard in a small bowl until smooth.
Cut each potato roll in half. Spread 1 teaspoon sauce on the cut side of each top and bottom bun. Place 1 to 2 tablespoons of shallots on the bottom bun. Add a meatloaf slice on top of the shallots and cover with a top bun (sauce side down of course). Serve immediately.
For quicker serving time, make your meatloaf ahead of time! Prepare and cook the meatloaf according to the recipe, cool the loaf completely in the pan, cover with foil, and refrigerate until ready to serve. Heat a large skillet over medium-high heat. Remove meatloaf from pan, cut into 6 even slices, and cook the slices in the skillet until warmed through and browned - flipping once. Assemble sliders as directed.