With nearly everything from strawberries to mangoes available year round coming upon truly seasonal rhubarb feels a bit special. It always feels like the right way to find it is to come across a rogue patch of rhubarb growing in the shade beside a farmhouse, or piled high on a stand in the farmer's market, one end still dusted with sooty black dirt and the other sprouting flat green leaves. However, the only time I have found rhubarb in San Diego is in the shelves of my local Whole Foods, slightly less rustic than what I hoped for. The aseptic stalks can usually be found near other more exotic fare like the daikon or the nopales, arranged neatly, stalks wiped clean and trimmed at the top. That is ok though because after being placed on a soft bed of hazelnut frangipane, blanketed with honey and vanilla, then stuck into a 400F oven until it's tops are nearly caramelized black and the bottoms are a jammy pale pink, they taste just as good.

I was in Paris for the a cold, mostly sunny, but at times rainy, mid-spring week in April. I love how seasonal the cooking  everywhere I ate, with white asparagus and rhubarb making appearances in nearly every menu I came across, nestled in green garlic aioli and coated with breadcrumbs or swirled into rice pudding speckled with vanilla beans (respectively). And most inspiringly, I did finally find my wild pile of rhubarb in a farmer's market in St. Germain. It was nestled in between deep purple beets and white-tipped French radishes, sitting precariously atop heads of bok choy. Sadly I had no kitchen in my teensy hotel room to make use of it so settled for snapping a picture on my iPhone and making my mind up to find rhubarb as soon as I got back home. It worked out ok.

Crostatas are one of my favorite pie-type desserts, there is no lattice-work or crimping to worry about and in my opinion, a perfect crust-to-filling ratio. And rhubarb and hazelnut are two flavors I ran into a lot during my week in Paris: rhubarb macarons, chocolate hazelnut praline spread on lacey buckwheat crepes, a slice of rhubarb almond tea loaf with my cafe noisette, golden hazelnut pastry cream inside a Paris-brest, and the aforementioned rhubarb rice pudding to name a few. So in a way this crostata is an ode to a perfect spring week in Paris, with sunny days, a bit of rain and a lot of rhubarb.

RECIPE:

RHUBARB & HAZELNUT FRANGIPANE CROSTATA

Makes 1 large crostata

INGREDIENTS:

Rye Crust:

• 2/3 cup AP flour
• 2/3 cup rye flour
• 1/4 teaspoon salt
• 1 tablespoon sugar
• 8 tablespoons of cold butter, cubed
• 1/4 to 1/3 cup of ice water
• 3/4 teaspoon of apple cider vinegar

Hazelnut Frangipane:

• 1 cup blanched toasted hazelnuts
• 1/2 cup brown sugar
• 5 tablespoons butter
• 2 tablespoons AP flour
• 1 egg
• 3/4 teaspoon salt
• 1/2 teaspoon pure vanilla extract
• Optional: 1 tablespoon hazelnut liquor (like Frangelico)

Assembly:

• 4 large stalks (about 1.5lbs) of rhubarb
• 1/2 cup of honey
• 1/4 teaspoon vanilla paste
• 1 egg
• 1 tablespoon of cream or milk

INSTRUCTIONS:

1. To make the crust: Mix together the flours, salt, and sugar together in the bowl of a food processor. Add the butter in and process until you have small pea-sized pieces. Add in the apple cider vinegar and 1/4 cup of the water into the dough. Process until the dough just comes together when pressed. If too dry add the remaining water in, one tablespoon at a time until it comes together. Remove, wrap in plastic wrap and chill for one hour. 
2. To make the frangipane: Meanwhile, combine hazelnuts and the sugar in the bowl of a food processor and process until well ground. Add in all the other ingredients and process until smooth. I like to add some hazelnuts in at the very end for some crunch, but this is up to you.
3. To make the pie: When you're ready to make the filling and assemble the pie, preheat oven to 400F.
4. Roll out the pastry dough to a ~1/4 inch thick rectangle on a non-stick mat for easy transfer. Spread the hazelnut frangipane over the surface of the pie, leaving about 1.5 inches of uncovered crust at the edges to fold over. Layer the chopped rhubarb over the top of the hazelnut frangipane. 
5. Mix the honey with the vanilla paste and generously brush over the rhubarb. Whisk the egg with cream for an egg wash and brush the edges of the crust with it. Top the crust with demerara sugar.
6. Bake in the oven for 35-45 minutes until the pastry is golden brown and the rhubarb looks caramelized on top. At 15 minutes, quickly remove the pie from the oven to brush more vanilla honey over the rhubarb. Note to check the pie at 25 minutes and if the rhubarb is already looking quite dark on top, cover it with foil to prevent it from scorching too much.
7. Best served with crème anglaise (I made mine with hazelnut milk, which explains why it has a more brownish tint).

Hazelnut frangipane recipe adapted from Martha Stewart, and rye crust from Yossy Arefi via Food52.

I like adding the creme anglaise to the pie but if you are feeling a bit lazy a generous layer of mascarpone mixed with brown sugar squeezed in between the hazelnut frangipane and the rhubarb is equally nice. Or for the lazy and mascarpone-less, there is always a scoop of ice cream. Best eaten warm out of oven, naturally.