As common as rhubarb is in much of the US, it is not a native plant to North America. European immigrants brought it here in the 18th century, after it was grown and used for centuries as a medicinal root in China, and spread throughout Asia and Europe over eastern trade routes.
Although commonly treated as a fruit in the kitchen, rhubarb is not a fruit at all, nor is it a vegetable. It is an herb, in the same family as buckwheat and sorrel, and although its leaves are big and flashy, they’re too toxic to eat. However, its stems, wantonly tart and colorful, become lusciously tender when cooked just long enough, and melt away to silky softness when cooked to their limit.
When paired with balsamic vinegar, rhubarb becomes a savory ingredient in a deeply flavored reduction (Rhubarb Balsamic Reduction). That reduction, paired with a local, seasonal mate, maple syrup, results in a smoky, sweet-tart glaze for roasted meats or vegetables (Maple Rhubarb Balsamic Glaze). Finally, when reunited with regional cousins ginger and buckwheat, rhubarb takes its pride-of-place in a familiar, homey dessert with a new twist.
In Britain, rhubarb and ginger have been paired in desserts and sweets for a very long time. Since the British brought rhubarb with them to North America, I decided to honor this tradition here. I used buckwheat honey in the filling, and buckwheat groats in the topping, because I like to combine plants from the same family in my dishes. I’ve found they often get along well in the kitchen, as these two did here.
Serve the crumble topped with vanilla custard or pudding, ice cream, whipped cream, or simply drizzle with heavy cream.
Use as much of the topping as you like on the crumble; toast the rest on a baking sheet in a 350 degree oven until browned, let cool, and store in an airtight container. It’s a great crunchy topping for yogurt, or ice cream.
1 1/2 lbs. rhubarb
1/2 teaspoon finely grated fresh ginger
1/2 cup granulated sugar
1/4 cup buckwheat honey
½ cup buckwheat groats
½ cup rolled oats
2 tablespoons chopped candied ginger
a pinch of salt
4 tablespoons cold unsalted butter
To make the filling:
1. Chop the rhubarb into ½ inch pieces (you need about 4 cups).
2. Combine the rhubarb, ginger, and sugar in a large saucepan and leave them to sit for 15 minutes, to begin to draw out the rhubarb’s juice.
3. Add the honey, and stir the mixture to coat the rhubarb with juice, and place the saucepan over low heat. Simmer it slowly, stirring frequently, until the rhubarb is tender, and enrobed with the sweet, thickened sauce, about 20 minutes.
4. Remove the pan from the heat and allow the filling to cool to room temperature. (The filling can be refrigerated until you’re ready to make the crumble, up to 3 days.)
To make the topping:
1.Toast the buckwheat groats in a 350-degree oven until they are browned and lightly crispy, and let cool.
2.Combine groats, oats, candied ginger and salt in a food processor, and pulse until finely ground. Add the butter, and pulse until evenly combined.
To assemble and bake crumble:
1. Grease a 9-inch pie plate.
2. Spread the filling evenly in the bottom of the pie plate. Distribute the topping evenly over the top of the filling. Bake at 375 degrees until bubbly, and the topping is browned, about 30-35 minutes. Cool on wire rack before serving.