Paris-Brest by America's Test Kitchen

Praline
1/2 cup sugar (3 1/2 ounces)
1/4 cup water
1 teaspoon lemon juice
1 cup hazelnuts, toasted and skinned
1/2 teaspoon salt
1 tablespoon vegetable oil

Pastry Dough
4 large eggs
8 tablespoons unsalted butter, cut into 16 pieces
1/2 cup whole milk
1/3 cup water
2 3/4 teaspoons sugar
3/4 teaspoon salt
1 cup (5 ounces) flour
2 tablespoons toasted, skinned, and chopped hazelnuts

Cream Filling
2 teaspons unflavored gelatin
1/4 cup water
1 1/2 cups half-and-half
5 large egg yolks
1/3 cup (2 1/3 ounces) sugar
3 tablespons all purpose flour
3 tablespoons unsalted butter, cut into 3 pieces and chilled
1 1/2 teaspoons vanilla
1 cups heavy cream, chilled
confectioners'sugar

Instructions
1. For the Praline
 Line rimmed baking sheet with parchment paper; spray parchment with vegetable oil spray and set aside.  Bring sugar, water, and lemon juice to boil in medium saucepan over medium heat, stirring once or twice to dissolve sugar.  Cook witout stirring until syrup is golden brown, 10 to 15 minutes.  Remove saucepan from heat, stir in nuts, and immediately pour mixture onto prepared b aking sheet.  Place baking sheet on wire rack and allow caramel to harden, about 30 minutes.

2. Break hardened caramel into 1-2o 2-inch pieces; process pieces in food processor until finely ground, about 30 seconds.  Add salt and vegetable oil and continue to process until uniform paste is formed, 1 to 2 minutes.  Transfer mixture to bowl, cover with plastic wrap, and set aside.

3. For the Pastry dough
Adjust oven racks to upper-middle and lower-middle positions and heat oven to 400 degrees.  dRaw or trace 8 inch circle in center of two 12 by 18 inch sheets of parchment paper; flip parchment over.  Spray 2 baking sheets with spray and line with parcment (keeping guide rings on underside.

4. Beat eggs in measuring cup or small bowl; you should have about 1 cup (dscard any excess over 1 cup). Heat butter, milk, water, sugar and salt in medium saucepan over medium heat, stirring occasionally.  When mixture reaches full boil (butter should be fully melted), immediately remove saucepan from heat and stir in flour with heatproof spatula or wooden spoon until combined and no misture remains on sides of pan.  Return saucepan to low heat and cook, stirring constantly, using smearing motion, until mixture is slightly shiny and tiny bead of fat appear on bottom of saucepan, about 3 minutes.

5. Immediately transfer mixture to food processor and process with feed tube open for 30 seconds to cool slightly.  With machine running, graduallyt add eggs in steady stream.  When all eggs have been added, scrape down sides of bowl then process for 30 seconds until smooth, thick, sticky paste forms.

6/ Transfer 3/4 cup dough to pastry bag fitted with 3/8 inch round tip.  To make enarrow inner ring, pipe single 1/2 inch wide circile of dough directly on traced guide ring on 1 baking sheet.  For large outer ring, squeeze out any excess dough in pastry bag and change pastry bag tip to 1/2 inch star tip.  Pout all remaining dough into pastgry bag.  Pipe 1/2 inch wide circle of dough around inside of traced guide ring on remaining baking sheet.  Pipe second 1/2 inch circle of dough around first so they overlap slightly.  Pipe thrid 1/2 inch circle on top of other 2 circiles directly over seam.  Discard any escess dough.  Sprinkle chopped nuts evenly over surface of ring.