20–23 cm / 8–9 inch ungreased aluminum tube or angel food pan
Small saucepan
Mixing bowls (including a large grease-free bowl for egg whites)
Stand mixer with whisk attachment or hand mixer
Whisk
Large spatula
Sifter or fine-mesh sieve
Skewer or thin knife
Offset spatula or thin knife (for releasing cake)
Long serrated knife (for slicing layers)
Ingredients
For the blueberry compote
300gfrozen blueberriesdo not thaw; fresh blueberries also work
75ggranulated sugar
60mlwater
2tspfresh lemon juicebottled is fine in a pinch
1–2tspcornstarchoptional, mixed with 2 tsp cold water if compote seems very thin
2tspcold waterfor cornstarch slurry (optional)
For the chiffon cake batter
5largeeggsseparated, at room temperature
100ggranulated sugardivided (about 70 g for yolks, 30 g for whites)
60mlneutral oilcanola, sunflower, or light olive
90mlmilkroom temperature (dairy or unsweetened non-dairy milk)
60gblueberry compotecooled to room temperature
1tspvanilla extract
115gcake floursifted
1 1/2tspbaking powder
1/4tspfine salt
For the meringue
5largeegg whitesreserved from above
1/4tspcream of tartaror 1/2 tsp lemon juice
30ggranulated sugarreserved for whites
For the blueberry whipped cream and assembly
360mlheavy cream or whipping creamwell chilled
30gpowdered (icing) sugarsifted
3–4tbspblueberry compotecompletely chilled
1/2tspvanilla extractoptional
80–120gfresh blueberriesfor decorating
Instructions
Make the compote: Add frozen blueberries, sugar, and water to a small saucepan. Bring to a gentle simmer over medium heat, stirring occasionally, until berries release juices (about 5–7 minutes). Lightly mash some berries, then simmer 3–5 minutes more until slightly syrupy; stir in lemon juice. If thin, add cornstarch slurry and simmer 30–60 seconds. Transfer to a shallow bowl; cool to room temperature, then chill.
Prepare oven and pan: Preheat oven to 165–170°C / 325–340°F with a rack in the lower-middle position. Use a completely clean, dry 20–23 cm / 8–9 inch ungreased aluminum tube (angel food) pan—do not grease or line. Separate eggs; put yolks in one bowl and whites in a large grease-free bowl.
Mix yolk batter: Whisk yolks with about 70 g sugar until lighter. Whisk in oil until emulsified, then whisk in milk, 60 g cooled compote, and vanilla. In a separate bowl, sift together cake flour, baking powder, and salt. Add dry ingredients to yolk mixture in two additions and mix just until smooth and no dry pockets remain.
Whip meringue: Add cream of tartar to egg whites. Beat on medium until foamy, then gradually sprinkle in remaining 30 g sugar. Increase to medium-high and whip to glossy medium-stiff peaks (peak stands with a slight curl at the tip).
Fold: Fold 1/3 of the meringue into the yolk batter with a large spatula. Fold in the second third, then the final third, until no white streaks remain and batter looks airy.
Bake: Pour batter into the ungreased tube pan. Run a skewer/thin knife through once or twice to pop large air pockets; smooth the top. Bake 40–50 minutes, until golden, springs back when pressed, and a skewer near the center comes out mostly clean with a few moist crumbs (tent with foil late in baking if browning too fast; don’t open oven during the first 25 minutes).
Invert and cool: Immediately invert pan onto its legs or over a sturdy bottle neck so cake hangs upside down. Cool completely, at least 1 1/2 hours. Release with a thin offset spatula/knife around inner and outer edges and under the bottom; turn out onto a serving plate.
Make blueberry whipped cream: In a chilled bowl, whip cold heavy cream with powdered sugar and vanilla (if using) to soft peaks. Add about 3 tbsp chilled compote and whip just to smooth medium peaks. Adjust with more compote or a little sugar to taste.
Assemble: Optionally slice cake horizontally into 2 layers. Spread a thin layer of compote (about 1/4–1/3 cup) on the bottom layer, leaving a border; spread whipped cream over. Replace top layer. Frost top (and sides if desired) with remaining whipped cream, swirl decoratively, and decorate with fresh blueberries. Chill 30–45 minutes before slicing.