Gnocchi a la Parisienne

Fit pastry bag with 1⁄2-inch round tip. Beat eggs in 2-cup liquid measuring cup.

Bring 3⁄4 cup water, 4 tablespoons butter, and 3⁄4 teaspoon salt to boil in small saucepan over medium heat, stirring occasionally. As soon as mixture boils, remove saucepan from heat and stir in flour until incorporated. Return saucepan to low heat and cook, stirring constantly, using smearing motion, until mixture looks like shiny, wet sand, about 2 minutes.

Immediately transfer mixture to food processor. Add Gruyère and pepper and process, with feed tube open, for 10 seconds. With processor running, gradually add eggs in steady stream. When all eggs have been added, scrape down sides of bowl with rubber spatula. Continue to process until smooth, thick, sticky paste forms, about 30 seconds longer.

Fill prepared pastry bag with warm mixture. Twist top of bag to close and let rest at room temperature for at least 30 minutes or up to 1 hour.

Lightly grease rimmed baking sheet. Bring 4 quarts water to boil in large Dutch oven. Reduce heat to maintain gentle simmer. Using 1 hand, hold pastry bag at 45-degree angle so tip is about 3 inches away from surface of water and squeeze bag to force dough out of tip. Using paring knife, cut off 3⁄4-inch lengths and let them fall into water. Continue to pipe until 20 to 30 gnocchi are in pot. Simmer until gnocchi float and are slightly firm, about 2 minutes. Using spider skimmer or slotted spoon, transfer gnocchi to prepared sheet. Repeat until all dough is cooked (4 to 6 batches). (If not proceeding immediately, allow gnocchi to cool completely. Transfer to airtight container and refrigerate for up to 3 days. Alternatively, freeze on sheet until solid, then transfer to zipper-lock bag and freeze for up to 2 months; sauté from frozen, adding 1 to 2 minutes to sautéing time.)

Melt 3 tablespoons butter in 12-inch nonstick skillet over medium heat. Add all gnocchi and shake skillet gently until gnocchi fall into single layer. Cook, tossing every 2 minutes, until gnocchi are golden brown and slightly puffed, about 6 minutes. Return cooked gnocchi to sheet.

Melt remaining 2 tablespoons butter in now-empty skillet over medium heat. Add tomatoes, olives, thyme, and remaining 1⁄4 teaspoon salt and cook, tossing occasionally, until tomatoes start to soften, about 2 minutes. Add lemon juice and gnocchi to skillet and gently stir until gnocchi are evenly glazed. Off heat, add arugula and stir until it just starts to wilt, about 15 seconds. Top with chives and serve immediately, passing Parmesan separately.