Mix the warm milk with 1 tablespoon of sugar, the yeast, and 2 tablespoons of flour. Stir until the mixture becomes smooth and slightly thickened. The milk should be comfortably warm to the touch—not hot—so it activates the yeast without damaging it.
Let it rest for 10–15 minutes, until it foams and rises. A bubbly surface and expanded volume indicate that the yeast is active and will give the dough its soft, airy texture.
2️⃣ Make the dough
In a large bowl, place the flour, sugar, salt, eggs, vanilla, and the prepared pre-ferment. Combine them gently to begin forming the dough. At this stage, the mixture will look rough and slightly sticky, which is expected.
Start mixing and, lastly, add the melted butter. Incorporating the butter at the end helps the dough absorb it more evenly and develop a smooth, supple texture. The butter should be melted but lukewarm, ensuring it blends easily without tightening the dough.
Knead the dough for 8–10 minutes, until it is elastic and soft. The dough should become glossy and stretchy, pulling away from the bowl or work surface with ease. Avoid adding too much extra flour; a slightly tacky dough will bake into a fluffier cake.
Cover the bowl and let it rise for 1 hour, until it doubles in size. A warm, draft-free place is ideal. The dough should look puffed and airy, with a lighter feel when gently pressed.
3️⃣ Prepare the crumble topping
Mix the flour, cold butter, and sugar with your fingertips until it forms loose crumbs. Rub the ingredients lightly, letting the butter create small, irregular clumps. Cold butter is essential here—it ensures the crumble bakes into crisp, defined pieces rather than melting into the dough.
(Optional) add vanilla. A few drops deepen the aroma and complement the cake’s vanilla base without overpowering the fruit.
Keep refrigerated while the dough rises. Chilling helps the crumble stay firm and maintain its shape during baking.
