Preheat your oven to 204 °C (200 °C). Line a baking sheet with parchment paper. Pierce each sweet potato several times with a fork, rub with 1 teaspoon of olive oil, and season lightly with salt.

Bake the sweet potatoes on the prepared sheet for 40 to 45 minutes, or until completely tender when pierced through the center with a knife.

While the potatoes bake, whisk together the mayonnaise, yellow mustard, and tomato paste with a pinch of black pepper in a small bowl until smooth to make the sauce. Set aside in the refrigerator.

Heat the remaining olive oil in a large cast-iron skillet over medium-high heat. Add the diced onion and ground beef, pressing the meat firmly against the hot pan with a sturdy spatula to create deeply browned, crispy smashburger-style edges.

Break the beef into smaller crumbles, add garlic powder, smoked paprika, remaining salt, and pepper, and sauté for another 2 to 3 minutes until fully cooked through. Remove skillet from heat.

Slice open the baked sweet potatoes lengthwise and gently fluff the interior flesh with a fork, creating a pocket for the filling. Generously fill each potato with the seasoned beef mixture and top with shredded cheddar cheese.

Return the loaded sweet potatoes to the oven for 3 to 4 minutes, or until the cheese is completely melted and bubbly.

Drizzle each stuffed potato generously with the chilled burger sauce, scatter chopped dill pickles and fresh chives over the top, and serve warm.