The key to a toothsome alt-grain polenta is blitzing the grains for less time than you might think—about half of the millet should still be intact. If you go too far with it, the finished dish will have a gummy texture.
- ⅓ cup grapeseed or other neutral oil
- 3 scallions, thinly sliced, plus more for serving
- 2 medium leeks, thinly sliced (white and light-green parts only)
- 2 garlic cloves, thinly sliced
- 1 tablespoon plus 1 teaspoon white miso
- Freshly ground black pepper
Pulse millet in a blender or food processor until about half of grains are broken. Transfer millet to a small bowl; set aside. Rinse out blender.
Heat grapeseed oil in a small saucepan over medium-high until hot. Add 3 sliced scallions and let sizzle just until green parts darken slightly, about 1 minute. Transfer to blender and let cool. Purée until very smooth.
Heat olive oil in a large saucepan over medium. Add leeks and garlic and cook, stirring often, until very soft, 8–10 minutes. Add broth and miso and whisk to combine. Bring to a simmer and whisk in reserved millet; season with salt. Bring to a boil, then reduce heat and simmer, uncovered, stirring occasionally, and adding more water by ¼ cupfuls to loosen if needed, until mixture is thick and grains are tender, 40–45 minutes. Taste and season with salt if needed.
Divide millet polenta among bowls. Top with scallion oil, more chopped scallions, and black pepper.
Do Ahead: Scallion oil can be made 1 week ahead; cover and chill.