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1
Preheat oven to 350F.
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2
Line 2 (15x10x1-inch) baking pans with foil; spray with cooking spray.
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3
Place cake mix, eggs, 1-1/3 cups water and 1/3 cup of the sour cream in large bowl.
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4
Beat with electric mixer on low speed 2 minutes; scrape bowl.
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5
Beat on medium speed an additional 2 minutes.
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6
Pour evenly into prepared pans.
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7
Bake 15 to 18 minutes or until toothpick inserted in centers comes out clean.
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8
Cool completely.
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9
Beat remaining 2/3 cup sour cream and powdered sugar in large bowl with wire whisk until well blended.
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10
Add whipped topping; mix well.
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11
Set aside.
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12
Toss strawberries and blueberries in separate bowl; set aside.
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13
Cut out 2 cake circles from cake layer in each pan, using a 6-inch saucepan lid.
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14
(You will have a total of 4 cake rounds.)
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15
Place 1 of the cake rounds on large dessert plate; spread with 1/2 cup of the whipped topping mixture.
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16
Top with 1/2 cup of the berry mixture and an additional 1/2 cup of the whipped topping mixture.
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17
Cover with a third cake round.
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18
Repeat layers of whipped topping mixture and berry mixture; top with remaining cake layer.
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19
Spread top with remaining whipped topping mixture.
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20
Garnish with fresh mint and additional berries, if desired.
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21
Refrigerate until ready to serve.
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22
Store leftover dessert in refrigerator.
