Step 1

Line a 9 1/2" x 12" quarter sheet pan with parchment paper, clip the two long sides in place so that the parchment can be used later to lift the tart out of the pan.

Step 2

In a stand mixer with paddle attachment, beat the sugar, butter and vanilla bean paste for 5 minutes, or until light in color. Add the flours and salt and mix on low for 20 seconds, scrape the bowl down and mix again on low for 10-20 seconds until the ingredients are just incorporated. The mixture will be very crumbly.

Step 3

Scoop out 1 C of the mixture and set aside for the crumb top. Pour the remaining crumbly flour/butter mixture into the prepared sheet pan and press the mixture into pan to create a level, flat crust, making sure the corners are well covered. Press the mixture up and onto the sides of the pan just below the rim. Refrigerate for 20 minutes. Preheat oven to 350F.

Step 4

Bake crust for 30 minutes or until light and golden. Rotate the pan 1/2 way through baking.

Step 5

Set up a bain marie by filling a 4 quart sauce pan 1/2 full with water. Bring water to steaming, not to a boil. A stainless steel bowl will need to fit in the bain marie, touching the water, without touching the sides. A double boiler system works well too. Have ready a fine mesh strainer and bowl for straining the curd.

Step 6

In the stainless steel bowl, add the sugar and yolks. Whisk briskly and immediately place bowl in ban marie. Continue whisking until mixture is viscous and sugar is melted. Add the zest, orange juice, vanilla bean paste and salt. Stirring frequently, cook to 175F or swipe your finger across the back of a spoon. When your finger leaves a clear path on the back of a spoon without any curd running into that clear path, the curd is ready. Be sure to watch the water as it needs to remain steaming, not boiling.

Step 7

Strain the curd into a bowl and stir in the the butter, 1/2 tablespoon at a time, until it is fully incorporated.

Step 8

Cover the curd placing plastic wrap directly on the surface of the curd. Place in refrigerator until ready to use.

Step 9

If the baked crust developed any cracks, take a bit of the crumbly topping and gently patch the cracks.

Step 10

Pour the curd over the baked crust using an offset spatula to spread the curd evenly.

Step 11

Sprinkle the crumble topping over the curd distributing it evenly across the tart.

Step 12

Bake at 350F for about 35 minutes, rotating the pan 1/2 way through baking. You'll notice the top will caramelize a bit.

Step 13

Remove from oven and cool completely before finishing.

Step 14

Once the tart is cool, unclip the parchment paper and gently lift the tart out of the pan using the parchment as handles. Place on large cutting board. Use a serrated knife to trim the edges off, to make clean edges (save for snacking!).

Step 15

Cut into bars or squares. For bars, cut into 1 1/2" x 2" pieces. For squares, 4" x 4". The serrated knife works well here, but instead of sawing all the way through, cut with firm pressure all the way through the tart.

Step 16

Sift confectioners sugar over the tart or serve with sweetened vanilla bean whipped cream. Serve at room temperature.

Step 17

Store in a lidded container in the refrigerator for up to one week.