Preheat oven to 380 degrees.

In a large dutch oven, heat olive oil over medium-high heat. Sear the short ribs on all sides, including the ends, until browned, approximately 2 minutes per side. Remove the meat to a clean plate and set aside.

Add the onion and garlic to the dutch oven and cook until the onions are translucent, approximately 3-4 minutes. Stir in the meat, spices, Guinness, and beef stock. Bring the mixture to a boil, then reduce to a simmer. Cook uncovered on the stove for 20 minutes.

Cover the dutch oven and cook in the oven for 2 hours, until the short ribs are fork tender and falling off the bone. Remove the meat to a plate to cool.

Place the dutch oven with the cooking liquid on the stove over high heat. Reduce the liquid by half. Rapidly whisk in cornstarch to ensure no clumps form. Continue reducing the sauce until it is thick.

Using your hands or two forks, shred the short rib meat. Add the meat to the thickened sauce. Stir to combine.

To assemble the sliders, place the bottom half of every toasted potato roll on a clean baking sheet. Add approximately 2-3 Tbsp of short rib meat coated in the sauce to the bottom half of every bun. Top each slider with cheddar cheese. Melt the cheese under a broiler set to high (watch them closely!) for approximately 30 seconds. Add pickles and the top half of every bun. Serve immediately (with more Guinness!).