Meet the Team


Our professional and dedicated team is committed to our community and to providing exceptional hospitality.

Dan Thiessen

Co-Owner & Managing Partner


A native of eastern Washington, Managing Partner Dan Thiessen was raised on a cattle ranch in Asotin, 2 hours east of Walla Walla. As a graduate of the Culinary Institute of America, his 25 year career has included kitchens in Switzerland, Aspen, Coeur d’ Alene, Seattle and Walla Walla. In 2018, Dan partnered with Paul Mackay and Philip Christofides to open Walla Walla Steak Co. and Crossbuck Brewing in the historic Walla Walla train depot, and recently announced plans for a
new location set to open in Woodinville in 2022. Dan and a team of partners purchased Yellowhawk Resort (formerly Basel Cellars Estate) in 2020 and will continue to operate the iconic property as an exceptional wine country lodging and event location and sparkling house winery, while developing plans for further expansion. Dan and his wife Melissa are the proud parents of three sons and are active in the Walla Walla community, as well as operating the Asotin cattle ranch and their own farm and vineyard in Walla Walla.

George Anne Robertson

Wine Maker


Winemaker George-Anne Robertson is inspired by the Helen Keller quote, “Life is a daring adventure, or nothing,” and her path to Yellowhawk has included some adventure along the way. After served as the estate director at Walla Walla Vintners after graduating from the Institute for Enology and Viticulture at Walla Walla Community College. She always dreamed of becoming a sparkling winemaker. When the new ownership team at Yellowhawk made the decision to become to a
sparkling house, George-Anne knew she had found the perfect opportunity to create something special new and unique.

George-Anne grew up in Saskatchewan, Canada in a small agricultural community called Melville and says her close family is a strong force and touchstone in her life. She is also the proud mother of two grown children, Haley and Clyde. George-Anne renews her energy in nature and is an avid hiker, trail runner, cyclist and Nordic skier. She loves to entertain, especially with a glass of crisp sparkling wine in hand.

Jim Kiefer

General Manager


Jim has built his career in the hospitality industry with a focus on creating a culture where people feel welcome and can come in and celebrate. That guest-focused perspective is what brought him to Walla Walla Steak Co. at the very beginning and is how he has contributed to its success. He will bring that same philosophy to Yellowhawk Resort and to create an experience where guests can come and get away from their everyday life and let his team take care everything else.

Prior to joining the company, Jim owned and operated a steak and seafood restaurant in Steamboat Springs, CO and then moved to Bend, OR where he served as general manager of the Bos Taurus steakhouse. Jim and his wife, Emily and their daughter Zoe enjoy time in the mountains fly fishing, skiing, and biking.

Shannon Stegeman

Hospitality and Events Director


Shannon Stegeman is known for her love of celebrations and bubbly personality, so her role as Hospitality and Events Director at Yellowhawk Resort and sparkling winery is a perfect fit. Shannon joined Yellowhawk in June 2021 after living in Napa Valley, CA and serving as the Events Operation Manager at Farmstead and as a Wine Educator at Cakebread Cellars. She also recently passed the WSET Level 2 exam with distinction, so she brings a wealth of wine knowledge and expertise to her new role.

Shannon was born and raised in Boulder, CO as the oldest of six children. She lived in San Diego, CA and Napa Valley before moving to Walla Walla with her partner and aspiring winemaker, Stephen.  Enjoying food and wine are Shannon’s passions. She loves to cook, as well as support local restaurants and markets. Her favorite travel locations are Italy and beach vacations, and she is looking forward to visiting the Champagne region of France.

Stephen Toschlog

Executive Sous Chef


Mariano Diaz

Vineyard Foreman


“I love showing up to work every morning, there’s a great vibe, incredible people, and I enjoy seeing the fruit of our work every day on the estate grounds and in the vineyard.”

“I was born in Michoacán, Mexico and raised in Walla Walla, where my family moved when I was 2 years old. Not long after graduating from Mac-Hi I began working at Basel Cellars.

I grew up in the valley and spent a lot of time in the orchards as a young man. Prior to Basel I worked for Appellation Management Group, it was a great experience getting to know the technical and scientific aspects of plant growth and management, particularly fruit. With the continued growth of the wine industry, I chose to set my sights on vineyard management, and began pursuing a career taking care of vineyards. I struck gold in 2010 when I was hired by Basel Cellars to assist in the vineyard.Since that time I’ve learned a great deal about wines, and how it truly does begin on the vine. We take great care to ensure the winery receives the best possible fruit, and are very hands-on throughout the process. I’m always thrilled to see the entire sequence unfold, and find myself continually impressed with the people that guide a process that I’m so fortunate to be a part of.”

Tony McGuire

Facilities and Maintenance Director