There’s so much I could say regarding tips for best foam but I’ll just summarise:
15-30ml of soda in the mix is ‘all’? & cream/fat is death to egg white. Add cream after mixing (milkshake machine is also advised then shake with a large format ice block after that) Lastly, to elevate foam above the glass, add soda or more mix with a narrow neck squirty type sauce bottle after patiently waiting 3min approx for foam to settle (preferably in the fridge).