"Everyone says that it's such a blur after it happens," says Harris of becoming parents to fraternal twins Harper Grace and Gideon Scott, born Oct. 12 via surrogate. "I find myself constantly just trying to wrap my mind around it."
After almost seven years together, Harris, 37, and Burtka, 35, began the surrogacy process and were "thrilled" to discover they were having fraternal twins.
"We inserted two eggs, one with my sperm, one with David's sperm and they both took," says Harris. Holding their children in the delivery room shortly after their birth was "just absolute joy," says Burtka. "We had two babies that we made. With help."
The family just moved into a "more kid-friendly" home in the Hollywood Hills and the twins have a new nursery with an old-school Disney theme park décor. "Harper has been fussy but Gideon is the easiest baby in the world," says Burtka. "They're just now starting to recognize us and smile."
"I just love the way they smell. And we can use them as an excuse to get out of almost anything," adds Harris, jokingly. "That's cleared the calendar in a good way."
For more of Harris and Burtka's interview, including exclusive photos of their twins, pick up this week's issue of PEOPLE on newsstands Friday