STRAWBERRY RHUBARB CRUMBLE WITH VANILLA CUSTARD SAUCE

makes one 9” skillet cake
 
For the custard sauce-
 
3 large egg yolks
pinch of salt
½ cup whole milk
½ cup heavy cream
⅓ cup granulated sugar
½ vanilla bean, split, seeds scraped with paring knife
 
In a medium bowl, whisk together the egg yolks and salt. In a medium saucepan, bring milk, heavy cream and sugar to a simmer over medium heat. Slowly pour the hot milk mixture into the egg yolks, whisking constantly. Transfer the milk/cream/egg mixture back into the saucepan and cook,, stirring constantly, until the custard thickens and coats the back of a spoon.  Remove from the heat and strain the custard through a fine mesh strainer. Whisk in the vanilla bean seeds. Set the bowl of custard over a large bowl filled with ice and water, stirring occasionally until cool. Remove from over the ice bath, cover the custard with plastic wrap and refrigerate.
 
For the crumb-
 
1 cup white-whole wheat flour
½ cup + 2 tablespoons rolled oats
½ cup firmly packed brown sugar
2 tablespoons sugar
½ tsp. ground ginger
½ tsp. cardamom
¼ tsp. kosher salt
½ cup plus 1 tablespoon, cool unsalted butter, cut into small cubes (cut the butter and let it sit out to soften slightly)
⅓ cup sliced almonds (or the nuts of your choice)
 
In a large bowl, whisk together the flour, oats, sugars, ginger, cardamom and salt. Add the butter pieces, rubbing the mixture together with your fingers until it becomes crumbly with some large chunks. Add the nuts and toss to combine. Cover and refrigerate until firm, at least half an hour.  
 
For the cake-
 
2 cups all-purpose flour
1 teaspoon baking powder
1 teaspoon ground cardamom
½ teaspoon kosher salt
1 cup granulated sugar
1 teaspoon orange zest
¾ cup (1½ sticks) unsalted butter
1 large egg
½ cup buttermilk
¾ pound rhubarb, leaves removed, rinsed, stems cut into ½” pieces
¼ pound strawberries, lightly rinsed, stems removed, cut into quarters
1 teaspoon vanilla extract
 
Preheat the oven to 350° F. Butter a 9-inch cast iron skillet.
In a medium bowl, whisk together the flour, baking powder, cardamom, and salt. Combine orange zest with sugar, rubbing the zest into the sugar with your fingers to release the orange oil. In the bowl of a stand mixer fitted with the paddle attachment, cream the butter and sugar until fluffy, scraping down the bottom and sides of the bowl. Beat in the egg. Add half of the dry ingredients, alternating with the buttermilk, then the remaining dry ingredients, beating on low until the batter is smooth. Fold in the rhubarb, strawberries, and vanilla. Pour the batter into the cast iron skillet and top with the crumb.
 
Bake for 45 to 50 minutes, until a toothpick tests clean when inserted in the center of the cake. Allow the cake to cool for several hours before serving with the custard sauce. Any leftover cake can be covered with plastic wrap and remain at room temperature for up to two days. Cover and refrigerate any leftover custard sauce.