Prepare the rhubarb – In a small saucepan over medium heat, combine the chopped rhubarb, water, and maple syrup. Simmer for about 10 minutes, stirring occasionally, until the rhubarb is soft and slightly syrupy. Remove from heat and set aside.
Cook the oatmeal – In a separate saucepan, bring the milk to a gentle simmer over medium heat. Stir in the oats, honey, cinnamon, vanilla extract, and a pinch of salt. Reduce heat to low and cook for about 5-7 minutes, stirring occasionally, until the oats are soft and creamy.
Toast the hazelnuts – While the oats cook, toast the hazelnuts in a dry skillet over medium heat for 3-4 minutes, shaking the pan occasionally, until they are fragrant and lightly browned. Let them cool slightly before roughly chopping.
Assemble the dish – Divide the oatmeal into two bowls, spoon the poached rhubarb over the top, and sprinkle with toasted hazelnuts.
Serve and enjoy – Serve warm with an extra drizzle of honey or maple syrup if desired.