Monday, July 03, 2006

Birthday Boston Cream Pie

A couple years ago, my husband (then boyfriend) asked me if I would make him a Boston Cream Pie for his birthday. My attempt - in the 90°, 99% humidity weather of a typical Massachusetts July, was less than successful. This year I tried again, with markedly better results. I fetched a Gourmet magazine recipe from Pretty basic - yellow cake, a custard filling (very similar to the pastry cream that went into the berry tart, actually) and a chocolate glaze for the top.

The cake:
3/4 c. unsalted butter
1 1/4 c. sugar
1 tsp. vanilla
2 eggs
2 c. cake flour [using cake flour, which is lower in protein than all-purpose, gives you a more tender cake]
2 1/2 tsp. baking powder
1/2 tsp. salt [omit if using salted butter]
3/4 c. milk

Cream together the butter, sugar and vanilla (with a hand or stand mixer) until fluffy. Add the eggs one at a time, beating until smooth after each addition. In a separate bowl, sift together the cake flour, baking powder and salt. Add the dry mixture to the butter mixture in about three portions, alternating with addition of milk. Pour equal amounts of batter into two greased and floured 9-inch round cake pans, and bake at 350°F for about 30 minutes (or, use one 9" springform pan and bake for 50-55 minutes). The cake should be golden with brown spots on top when done; check to make sure that a toothpick comes out clean. Let cool in the pan on a rack at room temperature for about 20 minutes before removing the cake from the pan [see assembly tips below].

The custard:
3 Tbsp. cornstarch
1/3 c. sugar
1 c. milk
3 eggs
1/2 c. heavy cream [you could use 1 1/2 c. half and half in place of the milk and heavy cream]
1/4 tsp. salt
1 vanilla bean, split lengthwise and with seeds scraped out [or add 1 tsp. vanilla at the end]
3 Tbsp. unsalted butter

The original recipe instructions are to whisk together all ingredients but the butter in a saucepan, bring to a boil over medium heat and continue whisking about 2 minutes until thick. Then remove from heat, remove the vanilla bean pod and whisk in the butter.

I chose to use the slightly more complicated method described in the tart recipe - combining the cornstarch, eggs and about 1/4 c. of cream; boiling together the rest of the ingredients (except the butter). Then take 2 Tbsp. of the boiling cream/sugar mixture and add to the eggs, whisk, strain, and then add the strained egg/cornstarch to the pan. Apparently, adding a bit of the boiling cream to the eggs will cause some undesirable bits of the egg to coagulate, which you can then strain out; this gives you a smoother custard than just boiling it all together.

Whichever method you choose, transfer the custard to a cool bowl and cover directly with a piece of plastic wrap to prevent a skin from forming. Let cool to room temperature before assembling.

Chocolate glaze: [It's easiest to make this after you've assembled the rest of the cake; see assembly notes.]
6 oz bittersweet or semi-sweet chocolate, broken into pieces
3 Tbsp. milk or cream
2 Tbsp. unsalted butter
1 1/2 tsp. light corn syrup
1/4 tsp. salt

Melt all ingredients except the milk/cream together in a double boiler/bowl over simmering water. I don't have a double boiler, so I used an old metal cake pan that happened to fit perfectly over my saucepan. The important thing here is to not let any steam escape from the pan of water - if any water mixes with the chocolate, the chocolate will seize and be gross. Add the milk/cream a little bit at a time until you reach a good pourable-but-not-too drippy consistency - 3 Tbsp. should be about right, but it's best to be a little cautious.

Assembly notes:
I was very lucky in that both my cake layers came out very cleanly and pretty flat, so I didn't have to do any trimming. I also had the bottoms of two springform pans to help me with the assembly - one to use as a platform for the cake and another to provide a nice surface to turn out the cakes from their pans. If you don't have springform pans, you can cut a circle out of a clean, sturdy cardboard box to serve a similar purpose.

Put the first cake layer right side up on your serving platter. Using a spatula, scoop ALL the custard onto the cake layer, making a big glob in the middle of the cake. Spreading from the middle makes you less likely to pick up crumbs, etc. Spread this evenly to about 1/4 inch from the edge of the cake - it will squirt out a little bit when you put the second layer on. Then, place the second cake layer, upside down (this gives you a flat top) on the custard; it's ok if you don't get it perfectly centered, you can just wiggle it into place.

Finally, prepare the chocolate glaze, and spoon on top in the same way you did the custard to avoid getting crumbs in the glaze. Boston Cream Pie is nice because you don't really have to frost the sides (which is a pain), you can just let the glaze drip artfully down the edges. Stick the cake in the fridge for a little bit so the chocolate will set up, or serve right away.

I was very excited at how well this cake turned out. The cake layers were tender and not too dense; the custard was delicious and at the perfect consistency (although, okay, using a whole vanilla bean probably wasn't necessary), and the chocolate topping was not too overpowering. Best of all, it tasted JUST LIKE a Boston Cream Pie! If I make this again, and I probably will - this seems like it might become a birthday tradition - I might make a 1 1/2 or double batch of the custard so that layer will be more substantial. But it's definitely wonderful as-is.

1 comment:

Rachel said...

this looks great! it is hard to do boston cream pie justice!