- 2 pounds rhubarb (trimmed, tough strings removed, cut into ½-inch pieces)
- ¼ cup sugar (use ⅓ cup for a sweeter flavor)
- 2 tablespoons cornstarch
- 1 tablespoon fresh orange juice
- 1 teaspoon orange zest
- ½ cup all-purpose flour (spooned and leveled)
- ½ cup brown sugar
- ½ cup whole rolled oats
- ½ cup crushed walnuts
- ½ teaspoon cinnamon
- ¼ teaspoon sea salt
- 6 tablespoons unsalted butter (cold and cubed)
- Vanilla ice cream (for serving)
