cook with gas
slang To have success in a particular activity. Once we dislodge that piece, we might cook with gas on this repair. That's a great idea—now you're cooking with gas!
cooking with gas
slang Having success in a particular activity. Once we dislodged that piece, we were really cooking with gas on this repair. That's a great idea—now you're cooking with gas!
cooking with gas
doing [something] exactly right. That's great! Now you're cooking with gas! I knew she was finally cooking with gas when she answered all the questions correctly.
cook with gas
Also, cook on the front burner. Do very well, make rapid progress. For example, The first half is finished already? Now you're cooking with gas, or Two promotions in two years-she's really cooking on the front burner! The first of these metaphoric phrases alludes to gas stoves, which began to replace slower wood-burning stoves about 1915. The variant, which alludes to something on a stove's front burner receiving more attention, is heard less often today. [Slang; 1940s] Also see back burner. 
cooking with gas
 in. doing exactly right. (Always with -ing.)  That’s great! Now you’re cooking with gas!