How should I M22 bring up our sexual experience with my close friend F22

So me and a close friend of mine have had an on and off relationship w/ eachother. Long story short were close friends and have known eachother since high school. We’ve had our ups and downs but at the end of the day we talk to eachother frequently and do as much as we can together. Love this woman she’s my best friend…but there’s one thing that’s hard to talk about due to the fact we never have really had a conversation about. For context things between us only ever get heated whenever were cuddling with eachother just things like grabbing her boobs, grabbing each other’s inner thigh, etc… We’ve had a couple conversations in the past about our relationship, first saying she’s not sure about a relationship and with the last time she said she thought she was lesbian. Almost a year later we’re cuddling again and she lets me rub her pussy over her clothes and she stroked my dick over mine. The only words exchanged was me asking permission to put my hand down there and her giving me the okay, that’s it. A couple weeks later I moved away for a 2.5 contract, we still stay in contact and I visit every few months and she even came to visit with her sister last week. Its been 1 year since then and I want to start an open conversation with her but I’m not sure how to start that.