Heat 1 tablespoon of oil in a large skillet or wok over medium heat. Add the onions and sauté for 2 minutes until softened.

Add the garlic, ginger, carrots, and mushrooms and sauté for 3 minutes, until fragrant.

Add the cabbage, kale, scallions, and salt and cook for another 3 minutes, until the vegetables are wilted and tender.

In a small bowl, whisk together the soy sauce, rice vinegar, and sesame oil. Pour the sauce into the skillet and toss to coat the vegetables evenly. Remove from heat and let the filling cool slightly.

Place a spring roll wrapper on a flat surface with a corner facing you, forming a diamond shape. Add about 2 tablespoons of the filling in a line across the center.

Fold the left and right corners over the filling, then fold the bottom corner up and roll tightly like a burrito. Brush a little water on the top corner to seal.

Heat the remaining 3 tablespoons of oil in the skillet over medium heat.

Working in batches, add the spring rolls seam side down, leaving space between each one. Cook for 2 to 5 minutes per side, turning occasionally, until golden brown and crispy all over. Each spring roll will take about 7 to 10 minutes total.