PORTLAND — Fresh rice noodles arrive in a floating jumble. They carry the broth up to you — intensely beefy, almost muscular, only lightly spiced — before they melt away. The kitchen makes these bánh phở every morning, steaming a milky white batter into sheets along the conveyor belt of a machine. And the result, especially if you’re used to the weight and resilience of dried rice noodles, is shockingly tender. Quynh Nguyen and Gian Carlo Reinardy, co-chefs and co-owners of the Paper Bridge, dreamed up their Portland, Oregon, restaurant when they first lived together in the Cầu Giấy district of Hanoi, the neighborhood where Nguyen was born and raised. Nguyen, a traditional Vietnamese dancer who traveled to perform, helped out occasionally at her family’s com binh dan, a buffet-style restaurant that specialized in affordable meals. Reinardy, a chef from Milwaukee, had been cooking in restaurants since he was 14.…