Melt butter in a pan and fry the garlic. Then add in the leeks and fry till the leeks are soft.
Next add in the flour and stir well before adding in the white wine and double cream.
Lastly add in the cheese and taste, season and taste.
Notes
TIP - Use any cheese you like but I prefer blue to go with steak (although I do not at blue cheese) The hubby, the boy and girl do. TIP - Add more or less wine, cream for more sauce. It is entirely your choice. TIP - Season AFTER you add the cheese and taste.