Boston Cream Pie

Make the Pastry Cream (Do This First)

1. Heat the milk: In a medium saucepan, warm the milk with 1/4 cup sugar and the salt over medium heat until steaming and just starting to bubble around the edges. Stir and scrape the bottom occasionally so nothing scorches.
2. Whisk the yolks: In a bowl, whisk egg yolks with the remaining 1/4 cup sugar until slightly lighter. Whisk in cornstarch until smooth.
3. Temper: Slowly whisk about 1/2 cup of the hot milk into the yolk mixture, then pour everything back into the saucepan.
4. Cook until thick: Whisk constantly over medium heat until it thickens and you see slow bubbles. Keep whisking for 30 to 60 seconds after bubbling begins so the cornstarch fully sets. If it is still loose, it probably did not boil long enough.
5. Finish: Remove from heat. Whisk in butter and vanilla. Strain through a fine-mesh strainer into a clean bowl (this fixes any tiny bits of cooked egg and keeps it silky).
6. Chill correctly: Press plastic wrap directly on the surface (touching the custard) and refrigerate until fully cold, at least 2 hours.
7. Stabilize: Right before assembling, whip 1/2 cup cold heavy cream to soft peaks and fold it gently into the cold pastry cream. This makes it lighter and helps it slice clean.

Bake the Cake Layers

1. Prep pans: Heat oven to 350°F (175°C). Grease two 9-inch round pans, line bottoms with parchment, then grease the parchment.
2. Dry mix: Whisk flour, baking powder, and salt in a bowl.
3. Whip eggs and sugar: In a stand mixer (or with a hand mixer), beat eggs and sugar on medium-high for 4 to 6 minutes until pale, thick, and ribboning. Beat in vanilla.
4. Heat milk and butter: In a small saucepan or microwave-safe bowl, heat milk, butter, and oil until butter is melted and the mixture is hot.
5. Combine: Gently fold the dry ingredients into the egg mixture in two additions. Then slowly drizzle in the hot milk mixture while folding, keeping as much air as you can.
6. Bake: Divide batter evenly between pans. Bake 20 to 25 minutes, until tops spring back and a toothpick comes out clean. If you like numbers, aim for about 200 to 205°F in the center.
7. Cool: Cool 10 minutes in pans, then turn out onto a rack. Cool completely before filling.

Make the Ganache

1. Chop chocolate: Put chopped chocolate in a heatproof bowl with a pinch of salt.
2. Heat cream: Warm cream until it is steaming and just about to simmer.
3. Melt: Pour hot cream over chocolate. Let sit 2 minutes, then stir gently from the center outward until smooth. Stir in butter if using. Let cool until thick but pourable, about 10 to 15 minutes. (This makes a soft, shiny cap. For a firmer, more set ganache, chill it a little longer before pouring.)

Assemble (Neat Layers)

1. Level the cakes: If needed, use a serrated knife to trim domes so the layers sit flat.
2. Add a barrier: Spoon the stabilized pastry cream into a piping bag (or zip-top bag). Pipe a thick ring around the edge of the bottom layer as a “dam.” This works best when your pastry cream is very cold and very thick. If yours feels softer, use a thin ring of buttercream instead, then fill the center with pastry cream.
3. Fill and smooth: Spread the remaining pastry cream in the center and smooth it flat.
4. Top and chill: Add the second cake layer, cut-side down if you trimmed. Chill the assembled cake 30 minutes so it firms up.
5. Glaze: Pour ganache in the center and gently nudge it toward the edges with an offset spatula. Let it drip naturally in a few spots if you like that look.
6. Set: Chill another 20 to 30 minutes to set the ganache before slicing.

Make-Ahead Plan

• 1 to 2 days ahead: Make pastry cream and refrigerate (plastic wrap touching the surface).
• 1 day ahead: Bake cake layers, cool completely, wrap tightly, and keep at room temp overnight or freeze for longer.
• Day of serving: Fold whipped cream into pastry cream, assemble, chill, then ganache and set.

Slicing Tips (Clean Layers)

• Chill first: Slice when the cake is cold. Warm custard is a saboteur.
• Use a serrated knife: Gentle sawing motion, do not smash.
• Wipe between slices: Dip the knife in hot water, wipe dry, slice. Repeat. This keeps the ganache top crisp and the custard line sharp.
• Photo trick: For extra clean edges, chill the cake 10 minutes after your first cut before taking your hero slice out.