Tuesdays with Dorie: Raspberry/Apple Cobbler

This week's Tuesdays with Dorie recipe was Mixed Berry Cobbler, chosen by Beth of Our Sweet Life.

Dorie's recipe calls for mixed frozen or fresh berries with a biscuit-dough topping. I fiddled around with the recipe and ended up with a part-whole-wheat topping and a black raspberry and grated apple filling. Served topped with leftover orange-flavored whipped cream from last week's cream puffs, it was a great treat.

Our freezer still holds a couple of gallon bags of frozen home-grown black raspberries. The new crop will be ripe very soon and it's time to use these up, so they were a natural choice for the filling. But I find that a raspberry-only filling is a bit seedy for our taste. I wanted to add something else. In the latest edition of Cooks' Illustrated magazine, I had noted a recipe for blueberry pie that called for adding grated apple to frozen blueberries to thicken the filling. Aha! I thought, I'll try that.

So, my final recipe for the filling called for one Granny Smith apple, peeled and grated, sprinkled with about 1 Tablespoon of lemon juice. Then I added enough frozen black raspberries to make a generous 5 cups. Our berries are somewhat tart, and then there's the tart apple and the lemon juice, so I upped the sugar to 6 Tablespoons. (Turns out I could have left it at 5.) Potato starch is my preferred thickener for pies and cobblers, so I turned to Shirley Corriher's wonderful book "Cookwise." The table on page 280 says that 4 teaspoons of cornstarch has the same thickening power as 2 1/4 teaspoons of potato starch. Using this, I calculated I'd need about 1 5/8 teaspoons of potato starch. I also added a sprinkle of salt. The rest of the ingredients were the same as Dorie's recipe. Since I chickened out on using the black pepper on the strawberry tarts, I decided to include it this time, but couldn't detect the flavor in the final result.

I made some changes to the biscuit dough topping, too. Jim and I both like part-whole-wheat toppings, so I used 2/3 cup of whole wheat flour. I also added 1/2 tsp. of vanilla extract and 1/2 tsp. grated lemon peel, for a touch more flavor, but did not increase the sugar. The dough was a little dry when it came together, and I added about 1 1/2 Tablespoons more milk. (A moist dough is best for biscuits.)

I decided to follow the cooking procedure from the Cooks' Illustrated cobbler I had made earlier this year, and cook the berries first until they were hot. Then the biscuit dough is added and you finish baking. (See picture and information at bottom of this post for more information about this recipe.)

I should have re-read the CI recipe more closely — it said to cook until the berries were bubbling around the edges. I only cooked until they were hot but not bubbling. I slid the round of dough on top of the berries using one of those flexible plastic cutting boards and sprinkled it with turbinado sugar. Then I turned the temperature up to 425 as per the Cooks' Illustrated recipe, and cooked for about 20 minutes. The dough looked done, but the berries were only beginning to bubble. Rats! I turned the temperature back to 375 and kept cooking, checking every 5 minutes. About 15 minutes later, the topping was deep brown and the filling was bubbling merrily out around the edges, but the center stubbornly refused to bubble. I was afraid to bake it any longer, the topping looked like it was going to burn soon, so I pulled it out.

(This picture shows why you should always put something underneath a berry pie or cobbler to catch those bubbling juices! The silicone mat made for easy clean-up.)

After cooling for about an hour, we sliced into it! Despite my worries, the filling was done even in the center. It had thickened nicely, in fact, perhaps too well for a cobbler. I think cobblers should be a bit runny so you can use the soft biscuit topping to soak up the juice. This filling would have been perfect for a pie instead. I guess the pectin in the grated apple and the potato starch together gave too much thickening power. I did like the way the grated apple sort of "melted" into the filling and yet made it a bit more smooth, reducing the "seedy" effect a little.

My other critique was that I thought there was too much topping and not enough filling. I'd increase the filling by 1/3 to 1/2 and decrease the topping to 2/3 or 3/4 of the original recipe.

Still, it was very good and disappeared fast!

Final conclusions? We still have more frozen raspberries—I see more cobblers in our future! For my next cobbler, I'll use the grated apple again, increase the total amount of filling to about 7 cups of berries (I'll need a deeper baking dish) and reduce the starch thickening. I'll keep the two-stage baking method but bake until the fruit bubbles around the edges. I'll use a part-whole-wheat biscuit topping recipe that calls for about 1 1/3 or 1 1/2 cups of flour, flavor it with a touch of vanilla and lemon zest, and sprinkle with sugar. We're both still "on the fence" about whether we like a smooth, one-piece topping like Dorie's recipe, or the "individual biscuit" style of the Cooks' Illustrated recipe. Both are good!

Hints for making biscuit dough:
Keep the butter very cold. Add enough liquid to make a moist, very slightly sticky dough—a moist dough rises better. Handle the dough as little as possible to avoid developing the gluten, which would make it tough. Bake in a very hot oven if possible for the lightest, fluffiest biscuits.
Hints for fruit fillings:
I find that 1 tablespoon of sugar to one cup of frozen berries suits our tastes. If I am using sour cherries I use a bit more sugar. Many recipes call for up to 2 tablespoons of sugar, which is much too sweet for us.

Here is a picture of the Cooks' Illustrated cobbler I baked in January of 2008, which gave me the idea for pre-baking the fruit.

The original recipe was for "Blueberry Cobbler" in Cooks' Illustrated magazine, July/August 2002. It is posted on their web site, but please note, the recipe is not free.