Preheat your Blackstone griddle to medium heat. Add the avocado oil and spread it evenly across the surface.
Score the sausages with shallow diamond cuts on all sides to help them cook evenly and absorb more flavor.
Place the sausages on the griddle. Cook for about 8–10 minutes, rotating a quarter turn every 2 minutes, until browned on all sides and heated through.
Add the sauerkraut to an open area of the griddle. Stir occasionally and cook until warmed through and lightly caramelized.
Butter the cut sides of the buns and place them cut-side down on the griddle.
Add a small splash of water to the griddle near the buns and cover briefly to steam, keeping them soft while lightly toasted.
In a small bowl, mix the mayonnaise and sweet & spicy mustard until smooth.
Assemble the dogs: spread the mustard-mayo sauce on each bun, add a sausage, and top generously with sauerkraut.
Serve hot and enjoy immediately.
Pro Tip
Scoring the sausage is optional, but it adds visual appeal and helps hold more flavor.