How to Make It
To prepare pastry cream, combine first 4 ingredients in a saucepan; stir with a whisk. Stir in milk, 1/2 cup half-and-half, and vanilla bean. Cook over medium heat until mixture boils, stirring constantly. Reduce heat to low; cook 1 minute or until thickened, stirring constantly. Pour into a bowl. Press plastic wrap onto surface; chill.
Preheat oven to 425°.
To prepare dough, weigh or lightly spoon flours into dry measuring cups; level with a knife. Combine 1 cup water, 3 tablespoons butter, and 2 teaspoons granulated sugar in a saucepan; bring to a boil. Reduce heat to low; add flours. Stir constantly with a wooden spoon until mixture is smooth and begins to pull away from sides of pan. Remove from heat; cool 5 minutes.
Place mixture in a large bowl. Beat with a mixer at medium speed 1 minute. Add 2 eggs and 2 egg whites, 1 at a time, beating well after each addition. Scrape sides of bowl; beat 1 minute.
Spoon into a pastry bag with a 1/2-inch round tip. Pipe 10 (4 1/2 x 1-inch) logs onto a baking sheet lined with parchment paper. Bake at 425° for 20 minutes.
Reduce oven temperature to 350°. Remove pan from oven; place another baking pan underneath to prevent overbrowning. Immediately return to oven, rotating pan. Bake an additional 25 minutes or until éclairs are lightly browned and sound hollow when tapped. Remove from pan, and place on a wire rack; pierce top of each with the tip of a knife (to allow steam to escape). Cool completely.
To prepare glaze, combine brown sugar, 1/4 cup half-and-half, 1 tablespoon butter, and syrup in a saucepan over medium-high heat; bring to a boil. Simmer 10 minutes or until reduced to 1/2 cup. Remove from heat. Stir in bourbon, vanilla extract, and half of salt. Cool 10 minutes.
Using a serrated knife, cut éclairs in half lengthwise. Discard vanilla bean. Fill bottom of each éclair with 2 tablespoons pastry cream. Spread 2 teaspoons glaze over top of each pastry (if glaze is too cool, microwave at HIGH 15 seconds or until spreadable). Replace tops, glaze side up; sprinkle evenly with remaining sea salt. Cover and refrigerate until ready to serve.