Make the Lilac Milk

1. Warm the milk to a gentle simmer; do not boil.

2. Remove from the heat, add the lilac blossoms, cover, and steep for 30–40 minutes.

3. Strain very well through a fine sieve or cheesecloth, pressing gently.

4. Cool completely. Measure out 1 1/4 cups (300 g) for the cake and reserve extra if needed.

Instructions

1. Preheat the oven to 350°F (175°C). Butter and line three 8-inch round cake pans with parchment.

2. Whisk together the flour, baking powder, baking soda, and salt.

3. In a large bowl or stand mixer, beat the butter, oil, and sugar until very pale and fluffy, 3–4 minutes. Add the eggs one at a time, beating well after each addition. Scrape down the bowl, then mix in the vanilla bean seeds and extract.

4. With the mixer on low speed, add the dry ingredients in three additions, alternating with the lilac-infused milk, beginning and ending with the dry ingredients. Mix just until combined — the batter should be smooth and fluid, not thick.

5. Divide evenly between the prepared pans and smooth the tops. Bake 22–26 minutes, until the cakes spring back lightly and a tester comes out clean.

6. Cool in the pans for 10 minutes, then turn out onto racks and cool completely.

Vanilla Buttercream

1. Beat the butter on medium speed until smooth and pale, about 1–2 minutes.

2. Add the powdered sugar in three additions, mixing on low just until incorporated. Scrape down the bowl well.

3. Add the vanilla and a pinch of flaky salt. With the mixer on low, add 4 tablespoons of heavy cream and mix until smooth.

4. Increase speed briefly and beat just until light and creamy. Add additional cream, 1 tablespoon at a time, until the buttercream is soft and silky.

Assembly

1. Level the cakes if necessary.

2. Place one layer on a serving plate and spread with a generous layer of buttercream (about 120–150 g).

3. Repeat with the second layer.

4. Top with the final layer and frost fully or semi-naked, smoothing softly. Flourish with fresh lilac petals.