Begin by preheating the oven to 425°F (220°C). Line a large baking sheet with parchment paper for easy cleanup and crispier results. Prepare the cauliflower by trimming it into uniform, bite-sized florets.
In a large mixing bowl, combine the non-dairy milk with apple cider vinegar or lemon juice. Allow this mixture to sit for about 2 minutes—this creates a tangy vegan "buttermilk" base. Stir in the flour, smoked paprika, garlic powder, onion powder, salt, and pepper. Mix thoroughly until a smooth, lump-free batter forms.
Pour the panko breadcrumbs into a separate shallow bowl. Working one piece at a time, dip each cauliflower floret into the batter, ensuring it’s well coated. Let any excess drip off, then roll it in the breadcrumbs, pressing gently so the coating adheres well.
Arrange the breaded florets on the baking sheet in a single layer without overlapping. Bake for 25 to 30 minutes, flipping each piece halfway through, until the coating turns golden brown and the cauliflower is tender inside and crisp on the outside.
While the cauliflower is baking, prepare the sauce by whisking together the vegan mayo, sweet chili sauce, sriracha, maple syrup (or agave), and garlic powder in a small bowl until well blended and creamy.
Once the cauliflower is done, allow it to cool slightly. Toss the crispy florets in the prepared sauce or serve it drizzled over the top. Finish with a sprinkle of chopped scallions and sesame seeds for a pop of freshness and added texture. Serve immediately for the best crunch and flavor.