Season the beef chuck generously with kosher salt and black pepper.

Heat avocado oil in a Dutch oven and sear the beef until deeply browned on every side.

Pour beef broth, BBQ sauce, Dr Pepper, and 2–3 tablespoons butter around the beef.

Cover the Dutch oven and braise at 300°F (150°C) until the beef is fall-apart tender.

Remove the beef from the pot and shred it into bite-size strands.

Return the shredded beef to the Dutch oven and toss it through the braising sauce.

Whisk sour cream, buttermilk, mayo, dill, one grated garlic clove, half the lemon juice, salt, and pepper until smooth.

Stir melted butter with the remaining grated garlic, parsley, remaining lemon juice, chili flakes, and salt.

Split the slider buns and toast them until golden.

Spread dill cream over the bottom halves of the toasted buns.

Pile saucy shredded beef onto the buns and cover it with habanero cheese.

Broil the open sliders until the cheese melts and bubbles.

Top the melted cheese with pickled jalapeños and crispy onion strings.

Close the sliders and brush their tops with cowboy butter before serving.