Who can a lease be assigned to?

Hello, done some reading around this question and need one bit of clarification. Think I saw something on this site before but can't seem to find it!

Scenario: I have converted a house into two flats with 2 seperatae entrances, utilities, gardens etc. Originally house had a freehold mortgage in the name of me and a partner.

I now need to split the title and create leases.

Is it possible to leave the freehold in the name of a partner and me and then assign both leases to myself?

Please help as I'm hearing various different things!