Chocolate Cake

Michael Eisenwasser

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A tender cocoa birthday cake with a gluten-free flour blend and lactose-free buttermilk, topped with a simple cocoa buttercream.

Prep 20 min

Cook 35 min

Serves 16

Gluten-free

Ingredients

Cake

• 1 3/4 cups (245 g) gluten-free flour blend
• 1/2 cup (45 g) unsweetened cocoa powder (natural or Dutch-processed)
• 1 1/2 teaspoons baking powder
• 1 1/2 teaspoons baking soda
• 1 teaspoon fine salt
• 2 cups (400 g) granulated white sugar
• 2 large eggs, room temperature
• 1 cup (240 ml) lactose-free buttermilk (or 1 cup lactose-free milk plus 1 tablespoon lemon juice, stirred and rested 5 minutes)
• 1/2 cup (120 ml) neutral oil (canola, grapeseed, or light olive)
• 2 teaspoons pure vanilla extract
• 1 cup (240 ml) boiling water

Simple Cocoa Frosting

• 1 cup (225 g) unsalted butter, softened
• 3 cups (360 g) powdered sugar
• 1/2 cup (45 g) unsweetened cocoa powder
• 3 to 4 tablespoons lactose-free milk
• 1 teaspoon pure vanilla extract
• Pinch of fine salt

Makes one 9x13-inch sheet cake, cut into 16 squares (4x4 grid). One serving is 1 square.

Instructions

Mix the Batter

1. Heat the oven to 350°F (175°C). Grease a 9x13-inch pan and line the bottom with parchment.
2. Whisk the flour blend, cocoa powder, baking powder, baking soda, salt, and sugar in a large bowl until no lumps remain.
3. Add the eggs, lactose-free buttermilk, oil, and vanilla. Beat with a hand mixer on medium speed for 2 minutes, scraping the bowl once.
4. Pour in the boiling water and mix on low until just combined. The batter will be very thin. That's correct.

Bake

1. Pour the batter into the prepared pan and tap the pan gently on the counter to release air bubbles.
2. Bake on the middle rack for 32 to 38 minutes, until a toothpick in the center comes out with a few moist crumbs.
3. Cool in the pan on a rack for at least 1 hour before frosting. Warm cake melts frosting.

Make the Frosting

1. Beat the softened butter in a large bowl for 2 minutes on medium speed until pale.
2. Sift in the powdered sugar and cocoa, then beat on low until absorbed.
3. Add 3 tablespoons of lactose-free milk, the vanilla, and the salt. Beat on medium-high for 2 minutes, until light and spreadable. Add the fourth tablespoon of milk only if the frosting feels stiff.
4. Spread evenly over the fully cooled cake with an offset spatula. Cut into a 4x4 grid for 16 squares.

Tips & Substitutions

• Layer cake variation. Divide the batter between two greased and parchment-lined 8-inch round pans. Bake at 350°F (175°C) for 28 to 32 minutes. Cool completely, level the tops with a serrated knife, and sandwich with a third of the frosting. Frost the top and sides with the rest. Cut into 16 wedges to keep cocoa within the Monash serve.
• Sheet cake is the easiest birthday version. Skip the layering, spread the frosting thick, and add sprinkles (plain sugar-and-cornstarch sprinkles are fine; avoid any "natural" brand that uses inulin or chicory root fiber as a bulking agent). Candles stick straight into the frosting.
• Coconut whipped cream frosting for dairy-free. Chill a can of full-fat coconut milk overnight. Scoop out the solid cream (leave the water behind), whip with 1/2 cup powdered sugar, 1/4 cup sifted cocoa, and 1 teaspoon vanilla until fluffy. Coconut products vary by type on Monash, so keep the topping to about 2 to 4 tablespoons per slice. Frost the cake close to serving; coconut whipped cream softens at room temperature.
• Lactose-free cream cheese frosting. Beat 8 oz softened lactose-free cream cheese (Green Valley Creamery) with 1/2 cup softened butter, 3 cups powdered sugar, 1/3 cup sifted cocoa, and 1 teaspoon vanilla. Richer than buttercream, still within dairy serves when the cake is cut into 16.
• No buttermilk on hand. Skip it entirely: use 1 cup lactose-free milk plus an extra 1/2 teaspoon baking soda. The crumb is slightly less tangy but still tender. Use lactose-free milk as the default so second slices and sensitive guests stay reliably low-lactose.
• Dairy-free cake. The cake itself has no dairy if you use the lactose-free-milk-plus-lemon-juice swap and oil (not butter). Pair with the coconut whipped cream frosting above for a fully dairy-free birthday cake.
• Add chocolate chips, carefully. Fold 30 g (about 3 tablespoons) of dark chocolate chips into the batter for extra chocolate punch. That's under 2 g per slice, well under the 30 g dark chocolate serve. Skip any "sugar-free" or keto chip; polyols (especially sorbitol, mannitol, maltitol, xylitol) commonly trigger IBS symptoms, and inulin and chicory root fiber are high-FODMAP.
• Sprinkles and decorations. Standard sugar sprinkles, sanding sugar, and royal icing decorations are fine. Gummy candies and licorice often contain high-fructose corn syrup or polyols, so check labels before dropping them on top.

Why This Works

Cocoa serve math. Cocoa powder is low-FODMAP at 8 g per serve. The cake uses 45 g of cocoa and the frosting adds another 45 g, for 90 g total split 16 ways: about 5.6 g of cocoa per slice. That leaves headroom under the 8 g threshold even after both cake and frosting are accounted for. Cut smaller pieces if you want seconds.

Lactose-free buttermilk trick. Real buttermilk is high-lactose and would push a cake past the dairy serve when shared among IBS guests. Lactose-free milk plus 1 tablespoon lemon juice curdles the same way, triggers the baking soda for lift, and keeps the crumb tender. Green Valley Creamery and Lactaid both work.

Sugar isn't a FODMAP. White sugar is sucrose: one glucose plus one fructose in a 1:1 ratio. The small intestine absorbs sucrose fully, so even 2 cups split 16 ways carries no FODMAP load. Powdered sugar is the same sucrose with a little cornstarch.

Oil over butter in the cake, butter in the frosting. Oil makes a moister, more tender crumb than butter and stays soft in the fridge. Butter in the frosting gives structure and the classic birthday-cake flavor. Butter is low-FODMAP at 1 tablespoon per serve; 1 cup split 16 ways is about 3 teaspoons per slice, well under the serve.

Gluten-free flour blend holds structure. The gluten-free flour blend already contains xanthan gum, so no extra binder is needed. Rice flour and starches hold a tender crumb without wheat's fructans.

Storage

Store frosted cake covered at room temperature for up to 2 days, or in the fridge for up to 5 days. Let refrigerated slices sit at room temperature for 20 minutes before serving so the frosting softens. For longer storage, freeze unfrosted cake layers wrapped tightly in plastic and foil for up to 3 months; thaw at room temperature before frosting. Frosted slices also freeze well individually wrapped for up to 1 month.

Not sure about an ingredient? FODMAP Tracker includes a database of 1,000+ foods with FODMAP ratings to help you cook with confidence.