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1
Preheat oven to 350 F. Grease three 8-inch cake pans. {note: pans should be at least 2-inches deep.} Line the bottom of each pan with parchment paper, butter the parchment and dust with flour.
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2
Toss blueberries with 3 Tablespoons of flour; set aside.
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3
In a medium-size saucepan, combine cream and loose leaf tea. Bring to just a simmer, remove from heat and cover. Let tea steep for about 5 minutes. Strain cream into a bowl, squeezing out as much as possible (you should be left with 118g of cream). Set strained cream aside to cool. Discard tea leaves.
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4
In a large mixing bowl, whisk together the flour, baking powder & salt; set aside.
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5
In a separate bowl, whisk together the room temp. cream/tea mixture & buttermilk; set aside. {note: make sure the cream has cooled completely before mixing with buttermilk.}
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6
In a large bowl, combine about 1 cup of the sugar with crushed basil. Use your finger to rub the basil into sugar until aromatic; whisk in remaining cup of sugar and set aside. In stand mixer bowl, fitted with whisk attachment, beat butter on medium speed until light & fluffy; about 5 minutes. Add sugar and continue beating for about 3 more minutes. Scrape down the edges of the bowl, add eggs one at a time, beating for one minute after each addition. Once all eggs have been incorporated, beat batter on med-high speed until light and voluminous (about 4-5 minutes).
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7
Switch over to a large rubber spatula. Fold in flour & buttermilk/cream mixture in three additions, beginning and ending with flour. Add blueberries and gently fold into batter till evenly dispersed.
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8
Divide batter evenly among prepared pans. Bake 25-30 minutes or until center is set and a thin knife comes out with a *slight* amount of crumb. {note: rotate pans half-way through baking time.}
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9
Remove pans from oven and place onto cooling rack. Cool cakes for about 20 minutes before removing from pan. Cool completely before frosting. {note: cakes can be made three day ahead of time. Cover with plastic wrap and refrigerate until ready to use.}
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10
In a medium size saucepan, combine the milk, cream loose leaf tea and thyme. Bring to just a simmer, cover, and steep for about five minutes. Strain into a bowl, squeezing out as much cream as possible (don't worry about having an exact measurement). Discard tea leaves and thyme sprigs.
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11
In a large heatproof mixing bowl, whisk together the sugar, cornstarch, eggs, and yolks; set aside.
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12
In a large saucepan, return the cream mixture to a slow simmer. Whisking constantly, slowly stream a small amount (about 1/2 cup) into the egg mixture. Stream in about another 1/2 cup, whisking constantly - this will temper the eggs so they won't scramble. Pour the warm, tempered, egg mixture into hot cream. Whisking constantly, simmer until thick and sluggishly bubbly; then cook for about 1 minute more - just to make certain the cornstarch is completely cooked out.
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13
Remove pan from heat and transfer mixture to stand mixer bowl. {note: if your eggs scrambled up a bit, no worries. Use a strainer to catch any mishaps.} Using the whisk attachment, set the mixer to low-medium speed until the bowl is room temperature and mixture is completely cool to the touch. This can take up to 20 minutes. Do not rush the process; mixture must be cool before continuing. If you have extra time, cover the surface of the cream with plastic wrap and refrigerate until ready to proceed - the stand mixer method is much faster.
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14
When pastry cream is completely cool, begin adding the room temp. butter cubes; about 1 Tablespoon at a time, with the mixer set on med-high. Once the butter has been added, repeat process with mascarpone cheese, adding about 1 Tablespoon at a time. {note: the mixture may appear to curdle halfway through adding butter, don't fret, keep mixing + adding...it will smooth out eventually.}
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15
Once all the butter and cheese has been incorporated, add the salt and whip until thoroughly combined. {note: at this point I added about 1/4 cup of blueberry preserves for colour.} You may use the frosting immediately or cover the bowl and refrigerate until needed. If you refrigerate the frosting, bring it to room temperature, then re-whip in stand mixer (using whisk attachment). If frosting is too cold, it will curdle - make sure it's completely reached room temp. before whipping.
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16
Don't be shy when frosting the cake layers; this recipe makes a lot of buttercream! You will more than likely have leftover frosting - which is fabulous on cookies, waffles, and toast! Please note: the frosting is temperature sensitive. If your house is humid, keep the cake in fridge until ready to serve.
