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1
Preheat oven to 325 degrees F.
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2
Grease an 8-inch-square baking pan.
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3
Toss blueberries with sugar and cornstarch.
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4
Set aside.
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5
To make crumbs, in a large bowl, whisk together sugars, spices, salt and butter until smooth.
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6
Stir in flour with a spatula.
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7
(It will look like a solid dough.
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8
).
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9
To prepare cake, in a small bowl, stir together the sour cream, egg, egg yolk and vanilla.
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10
Using a mixer fitted with paddle attachment, mix together flour, sugar, baking soda, baking
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powder and salt.
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12
Add butter and a spoonful of sour cream mixture and mix on medium speed until flour is moistened.
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13
Increase speed and beat for 30 seconds.
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14
Add remaining sour cream mixture in two batches, beating for 20 seconds after each addition, and scraping down the sides of bowl with a spatula.
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15
Scoop out about 1/2 cup of the batter and set aside.
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16
Scrape remaining batter into prepared pan.
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17
Spoon blueberries over batter.
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18
Dollop set-aside batter over berries; it does not have to be even.
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19
Using your fingers, break topping mixture into big crumbs, about 1/2 inch to 3/4 inch in size.
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20
They do not have to be uniform, but make sure most are around that size.
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21
Sprinkle over cake.
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22
Bake cake until a toothpick inserted into center comes out clean of batter, 45 to 55 minutes.
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23
Cool completely before serving.
