I agree with nsxtasy as to the best. I'd also add Sakezake in Grayslake if you want sushi, Bank Lane Bistro in Lake Forest, the Grille on Laurel in Lake Forest, and Sage Grille in Highwood for gourmet American.

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Sage Grille
260 green Bay Rd, Highwood, IL 60040

Sakezake
1227 N Il Route 83, Grayslake, IL 60030

Bank Lane Bistro
655 Forest Ave, Lake Forest, IL 60045