1 cup steel-cut oats
1/2 vanilla bean, split lengthwise
2 tablespoons light brown sugar (optional), plus more for serving
1/4 teaspoon ground cinnamon
1/8 teaspoon freshly grated nutmeg
1/8 teaspoon ground cardamom
Half-and-half or heavy cream, for serving
Coat the sleeve of a 5-quart slow cooker with nonstick cooking spray. Place sleeve in slow cooker and combine all ingredients in it; add 3 1/2 cups water and stir to blend. Set slow cooker to low and cook for 8 hours. Remove vanilla bean and scrape any remaining caviar into oatmeal. Stir well and serve with brown sugar to taste and a drizzle of half-and-half or heavy cream.