Hi Alain, Is this a cultivar? I thought L. lesliei var. minor had yellow flowers? I've heard of cultivar 'Witblom' with white flowers but not var. minor per se. Nice plant. I really like the large size of lesliei and the relative ease of cultivation.
'Witblom' is the white flowered form of var. minor. Collected by Des. Cole and numbered C006A. Lesliei is the largest headed Lithops I grow with correspondingly big flowers.