Forget about her megahit film My Big Fat Greek Wedding, or her TV series based on the movie, or her starring roles in Connie and Carla and My Life in Ruins. For actress, writer, and director Nia Vardalos, her greatest achievement was adopting a daughter in 2008.

Vardalos was hesitant to write Instant Mom (HarperOne, Apr.), her book about her experience with adoption, because she’s a private person and very protective of her daughter, but also because, as a comedian, she’s “not used to being serious.” Vardalos adds, “I wanted the book to be as funny as I find everything, but there were moments where I realized I had to tell the truth.” It took her and her husband, actor Ian Gomez, 10 years to finally become parents, and much of that time was filled with disappointments and sadness. The couple, married now for 20 years, was unable to conceive and then turned to fertility treatments that also ultimately failed.

Vardalos and Gomez decided to foster-adopt rather than use a surrogate or hire an attorney to arrange a private adoption, and it took less than a year after registering with the Foster Family Agency for them to be matched with their daughter, when she was three years old (she’s now seven). The research Vardalos put into finding the best adoption agency and preparing for what the process would require was determined and tenacious. “[Instant Mom] is the book I wished was out there when I didn’t want to feel so alone, and I wanted one place that would tell me how to do it,” she says. “There are other books, but I didn’t really know how to start looking. Not knowing how to do it scares us, because we hear stories of adoption groups that are less-than-credible, that will take your money, guarantee a match, and it doesn’t happen.” To ensure that Instant Mom provides all the essential and up-to-date information for potential adoptive parents, Vardalos wrote a 25-page appendix based on her research.

Born and raised in Canada in a large, boisterous Greek family—the type in which “your cousins are your siblings and your aunts are your moms”—Vardalos was encouraged from an early age to be generous. “My dad was the president of our church and my mom was the leader of the local Philoptochos, the Greek ladies auxiliary. We were raised to give back and do charitable work. It’s just a matter of fact,” she says. “So the book is a way of making sense of good fortune by helping others who want to become parents.” Vardalos has been the spokeswoman for National Adoption Day and National Adoption Awareness Month for several years.

She realized early on that rather than write a dry, specialized adoption book, she had to provide some of her personal backstory, to put her doggedness during the pregnancy and adoption processes—including 13 in vitro treatments—in context. This background information makes Instant Mom a memoir as well, and Vardalos pulls out all the humor stops—and affectionate name-dropping—in the telling. One story is about being invited to actress Rue McClanahan’s house for a Greek dinner party. When Vardalos and Gomez showed up, however, they were led to the kitchen and told to start cooking. They were shocked, but they put on aprons and persevered.

Instant Mom raises questions about the “nature vs. nurture” issue. How do adoptive parents know what kind of person their child will become? Vardalos says that her daughter is a self-confident, funny child who thinks for herself. “I truly believe that we make our own choices that lead us to what becomes our fate,” she notes. “So my daughter is who she is, and in our environment it was a perfect match. We have several gay friends. When my daughter was four years old she explained very clearly why everyone should be able to marry everyone. We encourage her to speak up and prove her point. It’s her nature and our nurturing environment that will make her become the person that she already is.”

Vardalos found it difficult to make the transition from writing screenplays to writing prose. “It was a daily struggle to not sugarcoat everything the way people in comedy want to do. We want you to laugh. We like laughter—it’s like french fries. But I cried my eyes out while I wrote the book.” Her social worker read and vetted Instant Mom before giving Vardalos an enthusiastic thumbs up. “She said to me, ‘Do you know how many kids you’re going to get adopted because of this book?’ And that gets me excited.”