Why This Recipe Works

Wellesley Fudge Cake originated roughly a century ago, when the founder of Wellesley College held that “pies, lies, and doughnuts should never have a place in Wellesley College.” Students honed their fudge-making skills in secret and produced some impressive fudge. When we tested recipes for Wellesley Fudge Cake, we found that decades of chocolate overload had desensitized the modern palate, and far more chocolate flavor was required of our recipe. We replaced some of the bar chocolate with cocoa powder bloomed in hot water to deepen its flavor. Traditional recipes called for “thick sour milk,” an ingredient we weren’t quite prepared to call for. Instead, we used buttermilk to give our cake a hint of tang. For our frosting, we found an unexpected solution in evaporated milk. Our frosting kept falling apart when we added chocolate to the warm sugar mixture—the heat was causing the fat in the chocolate to separate, a problem easily solved by adding butter and evaporated milk first to cool it down a bit.

Before You Begin

We prefer the deep color and balanced flavor of Dutch-processed cocoa powder in this recipe, but natural cocoa powder can be used. Although not traditional, two 9-inch round cake pans will work.

Instructions

for the cake

Adjust oven rack to middle position and heat oven to 350 degrees. Grease 2 (8-inch) square cake pans with baking spray with flour. Whisk flour, baking soda, baking powder, and salt together in bowl; set aside. In second bowl, whisk hot water, cocoa, and vanilla until smooth; set aside.

Using stand mixer fitted with paddle, beat butter and sugar on medium-high speed until light and fluffy, about 3 minutes. Add eggs, one at a time, and mix until incorporated. Reduce speed to low and add flour mixture in 3 additions, alternating with buttermilk in 2 additions, until combined. Slowly add cocoa mixture until incorporated.

Divide batter evenly between prepared pans. Bake until toothpick inserted in center comes out with few crumbs attached, about 30 minutes. Let cakes cool completely in pans, about 1 hour. (Cooled cakes can be wrapped in plastic wrap and stored at room temperature for up to 2 days.)

for the frosting

Heat brown sugar, ½ cup evaporated milk, 4 tablespoons butter, and salt in large saucepan over medium heat until mixture registers 235 degrees, 4 to 6 minutes, stirring occasionally.

Transfer brown sugar mixture to clean bowl of stand mixer. Fit mixer with whisk attachment, add remaining ½ cup evaporated milk and remaining 4 tablespoons butter, and mix on low speed until incorporated, about 30 seconds. Let mixture cool to 130 degrees, 10 to 15 minutes.

Add chocolate and vanilla to warm brown sugar mixture and mix on low speed until smooth, about 1 minute. Add confectioners’ sugar and continue to mix until fully incorporated and mixture is smooth, about 2 minutes longer, scraping down bowl as needed. Let frosting cool to 80 degrees, about 1 hour. (Leave whisk attachment in place. Crust will form on top of frosting; this is OK.)

Mix frosting on medium-high speed until smooth, about 1 minute. Place 1 cake layer on serving platter. Spread 1 cup frosting evenly over top, right to edge of cake. Top with second cake layer. Spread remaining frosting evenly over top and sides of cake. Refrigerate cake until frosting is set, about 1 hour. Serve. (Cake can be refrigerated, covered, for 2 days.)