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1
Preheat oven to 400F.
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2
CRUST: In a food processor, pulse flour, sugar, and salt.
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3
Add unsalted butter, pulse until mixture resembles coarse meal.
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4
Add 2 tablespoons ice water; process until mixture just comes together when squeezed (add more water if necessary).
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5
Add rolled oats; pulse to combine.
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6
Press dough onto bottom and 1-inch up sides of a 9-inch springform pan.
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7
Bake until golden, about 25 minutes.
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8
Remove sides of pan; cool crust.
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9
PASTRY CREAM: In a medium bowl, beat egg yolks and sugar until thick and light; beat in flour and cornstarch.
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10
In a saucepan, bring milk to a boil, whisking constantly, gradually add milk to egg mixture.
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11
Return mixture to saucepan.
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12
Bring to a boil, whisking constantly to prevent scorching, until mixture is thick and pulling away from sides of pan, 4-5 minutes.
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13
Stir in vanilla.
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14
Using a rubber spatula, press mixture through a sieve into a bowl.
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15
Cover surface directly with plastic wrap, and cool to room temperature in refrigerator.
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16
ASSEMBLY: Whisk cooled pastry cream until smooth.
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17
Spread evenly in crust; arrange grapes on top; create a pattern with the colors; press inches.
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18
Chill at least 2 hours and up to one day.
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19
just before serving dust with confectioners' sugar.,.
