Black Tea Cake with Blueberries & Lavender Cream

Make the Cake

1. Brew the tea using 1 tablespoon loose leaf black tea or 3 black tea bags with 1/2 cup hot water. Let steep for 20–30 minutes, then strain and cool.
2. Preheat the oven to 350°F. Butter and line two or three 8-inch round cake pans with parchment.
3. In a medium bowl, whisk together the flour, baking powder, baking soda, and salt. Set aside.
4. In the bowl of a stand mixer fitted with the paddle attachment, beat the butter, avocado oil, and sugar on medium speed until very pale and fluffy, 3–4 minutes.
5. Add the eggs one at a time, mixing well after each addition. Scrape down the bowl as needed, then mix in the vanilla.
6. In a measuring cup, stir together the cooled tea and milk.
7. With the mixer on low speed, add the dry ingredients in three additions, alternating with the tea mixture, beginning and ending with the dry ingredients. Mix just until combined.
8. Divide the batter evenly between the prepared pans and smooth the tops.
9. Bake for 25–30 minutes, until the cakes spring back lightly when touched and a tester inserted into the center comes out clean.
10. Cool in the pans for 10 minutes, then turn out onto a rack and cool completely before assembling.

For the blueberries

1. Place the blueberries, granulated sugar, lemon juice, cornstarch, vanilla bean seeds and salt into a large saucepan set over medium heat. Stir to combine. Heat, stirring often, until the sugar has completely dissolved and the berries are beginning to release their juices.
2. Increase the heat to medium-high. Continue to cook, stirring often, until the berries have slumped and the syrup is thick and reduced by a quarter, 5 to 7 more minutes. The syrup should also be thick enough to coat the back of a spoon.
3. Turn off from the heat and let the preserves sit at room temperature until cool, making sure to stir occasionally to prevent a skin from forming.

Lavender Mascarpone Cream

1. Combine the heavy cream and lavender, cover, and refrigerate for 12 to 24 hours.
2. Strain the cream through a fine-mesh sieve, pressing lightly on the lavender, then return the cream to the refrigerator until very cold. You should have about 200ml heavy cream.
3. In a mixing bowl, combine the mascarpone, lavender cream, powdered sugar, vanilla bean seeds, and salt.
4. Beat until the cream reaches soft to medium peaks. It should look thick, smooth, and pillowy enough to spread in thin layers.

If you prefer a warm infusion, place the cream and lavender in a small saucepan and warm just until steaming. Turn off the heat, cover, and let steep for 45 to 60 minutes, then strain and chill completely before using.

Salted White Chocolate Swiss Meringue Buttercream

1. Put the egg whites and sugar into the bowl of a stand mixer. Set it over a saucepan filled with simmering water (do not let the bowl touch the water). Heat, whisking constantly until the sugar is dissolved and the egg whites are hot to the touch, 160°F. Immediately remove, then set the bowl onto a stand mixer fitted with the whisk attachment. Whisk on high speed until thick and glossy, 5 to 7 minutes.
2. Switch to the paddle attachment. Slowly add the butter a tablespoon at a time, continue beating until smooth and silky, about 10–12 minutes.
3. Meanwhile, melt the white chocolate in a heatproof bowl set over a saucepan of simmering water. Remove from the heat and let cool until just warm to the touch.
4. With the mixer on low speed, pour in the melted white chocolate and mix until fully incorporated.
5. Add the flaky salt and mix briefly to combine. Use straight away.

Assemble the Cake 

1. Place one cake layer on a plate, cake board, or platter. Pipe or spread a border of buttercream along the edge — this keeps the filling in place. Spread a generous layer of the lavender mascarpone cream inside the border, then a layer of the blueberries. Top with the next cake layer and repeat, then finish with a plain cake layer on top. Store any leftover cream and blueberries in an airtight container.
2. Lightly frost the sides and top with a thin layer of buttercream to create a crumb coat. Refrigerate for 10–15 minutes to firm up, then frost with the remaining buttercream.