The six-month stint in Southern California proved to be formative for Paul. Upon graduating in 1991 he returned to LA to join Chef Joachim Splichal at Patina. It is here where Paul was exposed to a cuisine that was rooted in fine dining but also incorporated whimsical elements for a chic and discerning clientele. The experience gave Paul a strong foundation on which to develop his palette and refine his technique and skill. The daily rigors of the Patina experience were a proving ground for Paul as he was promoted to Sous Chef at Splichal's Bistro Classique; Pinot in Studio City.

In 1994 Paul relocated to San Francisco to be part of the team bringing Rubicon to national attention. Master Sommelier Larry Stone and restaurateur Drew Nieporent were guiding forces in Paul's career exposing him to the importance of wine and hospitality in the dining experience. In addition, Paul began shopping at various Bay Area farmers markets for the freshest produce, gaining valuable insight into sourcing the best ingredients for the restaurant. Paul worked his way through the ranks at Rubicon, eventually earning the title of Chef de Cuisine. The restaurant received numerous dining awards during his tenure including a James Beard Award and Wine Spectator's Grand Award for Excellence.

In 2000 Paul opened his critically acclaimed Belon. The rustic brasserie, featuring one of San Francisco's largest oyster bars was an instant hit. It was his expression of the rustic and soulful cuisine he had encountered during his travels in France.

As timeless as Belon was its time was not meant to be. Fate would push Paul to an even bigger stage as Chef of the bustling Grand Café. Paul resurrected this impressive brasserie with market fresh menus, innovative specials and classic signature dishes. Arenstam became the steady hand for the restaurant while assuming the fiscal and administrative responsibilities of Executive Chef.

The Grand Café was a perfect warm-up for Paul's current venture with famed Hotelier Chip Conley. As Executive Chef of Hotel Vitale and Americano Restaurant, Arenstam has guided this boutique property from pre-opening to its current status of being the premier waterfront hotel in San Francisco. Paul's Italian farm to table cooking is inspired daily by the neighboring Ferry Plaza Farmer's Market. It is at Americano that Paul has been able to connect his culinary voice with his belief in the sustainable food movement. In addition to his role as Executive Chef, Paul is the co-chair for CUESA's annual fundraising gala "Sunday Supper". Paul is also a member of Slow Food USA and had been active as a chef/collaborator for the 2008 Slow Food Nation event in San Francisco. In addition, Arenstam was chosen as a delegate to attend the 2008 Terra Madre and Salone de Gusto conference in Turin Italy. This landmark event brings together 6000 cooks, farmers, academics and change makers from around the world to advance the cause of good, clean and fair food systems. Paul's work has been featured in Food & Wine, Gourmet, Bon Appétit, San Francisco Chronicle, New York Times, The Wall Street Journal as well as numerous appearances on KRON 4's Bay Café. Paul resides in Piedmont California with his wife and Summer Kitchen Bake Shop founder Charlene Reis and their son Theo.