Make the gochujang dipping sauce: Stir together 2 Tablespoons gochujang, 1 Tablespoon soy sauce, 1 Tablespoon rice vinegar, 1 Tablespoon granulated sugar, and 2 teaspoons sesame oil in a small bowl or measuring cup. Set aside.
Prep the vegetables: cut 4-5 medium green onions into 1" lengths, peel and shred 2 medium carrots, trim the ends, and grate 1 small zucchini. Measure the prepped vegetables. You should have 2 1/2 to 3 cups total. If you have significantly more or less than this, you may have to adjust how much batter you use. If you decided to use other vegetables (eg. onion, sweet potato, mushrooms and/or peppers, make sure they replace other vegetables, and stay within 3 cups of vegetables). Add the prepped vegetables to a large bowl.
Mix up the batter: In a medium bowl, whisk together 1/2 cup all-purpose flour, 1/4 cup cornstarch, 1/2 teaspoon kosher salt, and 1/2 teaspoon baking powder. Whisk in 3/4 cup cold water. The batter will be thin.
Pour the batter over the prepped vegetables and toss to coat.
Heat 1 Tablespoon of canola oil in a medium to large non-stick skillet over medium-high heat. Note that if you have a large skillet (12" or larger), it is possible to cook all of the batter into one pancake, but it will be much harder to flip (in this case, use 2 Tablespoons of oil).
Add one-third to half of the batter to the hot skillet, spreading it into a circle. Cover the pan with a lid, and cook until the bottom of the pancake is browned and the top is beginning to set. Carefully flip the pancake, and continue to cook, uncovered, until browned on the other side.
Remove the pancake from the skillet and transfer to a cutting board. Cut into squares or triangles and serve with the gochujang dipping sauce. Repeat with the remaining batter, adding 1 Tablespoon of oil to the skillet before adding batter.