Preheat the oven to 425°F (218°C). Line a baking sheet with parchment paper, and spray with nonstick spray.

Start the Brussels sprouts. In a small mixing bowl or liquid measuring cup, whisk together the milk and rice wine vinegar. Set aside for 2 to 3 minutes.

Gather two medium mixing bowls. In the first bowl, add the flour and cornstarch. Pour in the milk and vinegar mixture and the soy sauce. Whisk the wet ingredients into the dry ingredients until fully combined and you have a smooth batter. In the second bowl, add the panko breadcrumbs.

Dip each Brussels sprout into the wet batter, coating completely, then put them into the panko breadcrumbs and coat completely. Place them on the prepared baking sheet. Repeat with all of the Brussels sprouts.

Spray the tops of the Brussels sprouts with more nonstick spray. Bake for 15 minutes. Flip the Brussels sprouts with tongs, and bake for another 15 to 20 minutes, or until they are crispy on the outside and tender inside.

While the Brussels sprouts bake, make the sauce. In a medium saucepan, whisk together the orange juice and cornstarch, making sure there are no lumps of cornstarch left. Add the vegetable broth, soy sauce, agave, rice wine vinegar, orange zest, garlic and ginger. Whisk to combine.

Heat the saucepan over medium heat, bring to a simmer, then reduce the heat to medium-low and simmer, whisking frequently, until the sauce thickens, 2 to 3 minutes. Add the sesame seeds and Thai chilies, if using, and simmer for another minute. Reduce the heat to low, and keep warm until the Brussels sprouts are done.

Transfer the Brussels sprouts to a large bowl, pour the sauce over them, and gently toss to coat.

Serve the Brussels sprouts over the rice, and top with green onions and more sesame seeds, if desired.