Rhubarb Lemon-Thyme Crumble with Cornmeal Streusel

To my palate, there’s only one dessert that beats a perfect fruit pie. And that’s a perfect fruit crisp or crumble–with or without bottom pie crust. That sweet, crunchy streusel topping is the perfect foil for tender, juicy peaches, apples, pears, cherries, raspberries, blackberries, blueberries and rhubarb.

But I’ve experienced mixed results with various streusel formulas over the years.

The Crunchiest Streusel Topping

As I explained in an earlier post, I was plagued over several seasons with soggy streusel toppings, even though the method I used has not changed over a couple of decades.

What I always did in the past was set the oven at 350°F, top the fruit filling with streusel, cover with foil, bake for 30 minutes, remove the foil, and bake for an additional 30 minutes. That used to work. Now, it produces a topping that melts into the fruit filling and doesn’t achieve the distinctive crunch that makes streusel so appealing.

So I took a wild leap of faith and baked the fruit filling alone for 30 minutes, uncovered it, added the same streusel, increased the oven temperature to 400°, and baked for an additional 25 minutes. Bingo, perfectly crunchy streusel!

But recently I discovered something perhaps even more critical to the crunchiest streusel topping ever. Simply cut back on the butter—so the streusel doesn’t melt into the filling. As you can see below, this streusel recipe utilizes only ¼ cup of butter to ¾ cup flour and cornmeal mixture. That’s a one-to-three ratio.

In the following streusel recipes I shared with you over the years, the ratio tends to be one-to-one or two-to-one.

• Apple Cranberry Deep Dish Pie with Toasted Walnut Streusel   (½ cup flour to ½ cup butter)
• Balaton Cherry & Lime Crisp with Toasted Almond Streusel   (1 cup flour to ½ cup butter)
• Ginger-Lime Peach & Blueberry Crisp with Toasted Hazelnut Streusel (1¼ cups flour to 10 tablespoons butter)
• Peach & Blackberry Pie with Coconut Streusel (1 cup flour to ½ cup butter)
• Rhubarb Apple Crisp with Toasted Hazelnut Streusel  (1 cup flour to ½ cup butter) 

Stay tuned for more on this front as I continue to experiment. In the meanwhile, you’re going to LOVE this rhubarb crumble—with the best streusel EVER.

Rhubarb Lemon Thyme Crumble with Cornmeal Streusel

Savory herbs and dessert? You bet. Rhubarb pairs beautifully with many traditionally savory herbs. I love it with thyme, sage, basil, and even rosemary. But how to make these flavors sing with such an assertive fruit?

On my first test for this crumble, I simply added a small handful of lemon thyme leaves to the rhubarb filling. The flavor was barely discernible. On the second test, I first processed the lemon thyme with sugar to release its volatile oils. Bingo.

NOTE   This cornmeal streusel is so heavenly that I make a quadruple batch and store the surplus in the freezer for ready use later over any berry, peach, or apple pie filling.

unsalted butter, for coating ramekins

Cornmeal Streusel

½ cup all-purpose flour
¼ cup yellow cornmeal (not coarse or polenta grind)
¼ cup sugar
finely grated zest of ½ lemon
¼ teaspoon fine sea salt
4 tablespoons unsalted butter, very cold, cut into 8 chunks
1½ teaspoons water, ice cold
1 teaspoon vanilla

Lemon-Thyme Sugar
¼ cup sugar
peeled zest of 1 large lemon (with no white pith)
small handful fresh lemon thyme or thyme (if stems are brittle, strip leaves and discard stems)

Rhubarb Filling
12 ounces (3 cups; 4 large stalks) trimmed, fresh rhubarb, cut into ½-inch chunks
¼ cup sugar
¼ cup brown sugar
2 tablespoons cornstarch
½ teaspoon fine sea salt
1 tablespoon fresh lemon juice

1. Center a rack in the middle of the oven, and heat to 375ºF.
2. Generously butter four 1-cup ovenproof ramekins. Reserve.
3. To make Cornmeal Streusel, in a processor fitted with the steel knife, blend flour, cornmeal, sugar, lemon zest, and sea salt.
4. Evenly disperse butter over dry ingredients in the workbowl, and pulse to combine.
5. Sprinkle water and vanilla over crumbs and pulse a few times to distribute. Test crumble by pressing a bit of it between your fingers. It should be just moist enough to clump and hold together.
6. Transfer to a small mixing bowl and reserve in the fridge.
7. To make Lemon-Thyme Sugar, in a mini processor fitted with the steel knife, pulse sugar, lemon zest, and lemon thyme until finely minced and well blended. The sugar will turn green.
8. To make rhubarb filling, in a medium mixing bowl, combine rhubarb, Lemon-Thyme Sugar, remaining ¼ cup sugar, brown sugar, cornstarch, and salt. Sprinkle on lemon juice and toss to distribute. Let sit for 15 minutes to allow rhubarb to begin to exude juice.
9. Divide filling between ramekins and top each with ¼ of the cold, pinched streusel bits.
10. To bake, arrange ramekins on a small, edged baking sheet, and bake at 375ºF. for about 30 minutes, until rhubarb is bubbling and streusel is crisp and golden.

Makes four individual crumbles.

Cookin’ with Gas (inspiration from around the web)

• Friday Pie Day! How Crumb, Crumble, And Streusel Toppings Make Every Pie Better | Epicurious
• Forget Pie, Love Apple Crisp: How to Make the Perfect Crumb Topping | Serious Eats

Copyright 2015 Susan S. Bradley. All rights reserved.