The 42-year-old actress stopped by Good Morning America on Monday, where she revealed that the Big Little Lies scene with the famed actress was "one of the top moments of my entire career."
"I might or might not have thrown an ice cream cone at Meryl Streep. In a scene, 'cause she made me mad," Witherspoon told co-host Robin Roberts. "It's going to be really good. And I think it's one of the top moments of my entire career. For real."
Above all, Witherspoon -- and Streep for that matter -- was most impressed with her aim. "And I hit her! Like, I nailed it!" she bragged. "She turned around and she was like, 'Yeah you got me.'"
When ET spoke to Witherspoon earlier this month, she reiterated how exciting the scene was to shoot.
"I did that!" she said at the time. "It's a top five moment in my career for sure."
"The amazing author Liane Moriarty wrote a follow-up novella that will never be published, but it gave us the basis for what is going to be the entire season two and it's so good," she said on GMA. "We were all just excited. I think you can tell when you watch the show that we just deeply love each other and we were having a lot of fun."
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Reese Witherspoon Calls Throwing Ice Cream at Meryl Streep a 'Top 5' Career Moment (Exclusive)
In addition to Big Little Lies, Witherspoon is also busy promoting her book, Whiskey in a Teacup, which drops Sept. 18.
"Well my grandmother used to say, 'Southern women are like whiskey in a teacup.' They're sort of beautiful and ornamental and put together on the outside, but they're really strong and fiery on the inside. And it's true!" she said of the book's title. "... I just learned a lot about being a part of a community and part of a family from my grandparents, who were just the biggest influence in my life."
On top of all of her projects, Witherspoon is also a mom of three -- Ava, 19, Deacon, 14, and Tennessee, 5 -- and currently in the midst of the busy back to school season.
"I see all the people post the cute pictures of their kids going to kindergarten, [but] mine won't let me take a picture. There's like a picture with [the sign] over his head," she lamented. "I've got one in kindergarten, one starting high school and one started college. I'm not going to lie, I was a little stressed. I was a little stressed this year."
"They approached me with the idea," she told Roberts. "This was this empowered moment, a feminist moment back in the early 2000s, wouldn't it be interesting to revisit her as she's turning 40 and she what challenges she's facing? It's really a good idea, so I'm excited!"
"I got to go to a meeting the other day and we talked about all the new plot points and all the characters and some returning characters and some new characters," she said at the time. "...I mean, I got so excited just in the meeting. I was like, 'This is going to be good.'"
Legally Blonde 3 is set to premiere on Valentine's Day 2020. In the meantime, check out ET's interview with Witherspoon: