To prepare Marinade:

Combine tamari and bourbon in a medium saucepan, bring to a boil. Whisk in other ingredients, reduce heat and simmer 5 minutes. Place steak and marinade in a zip-top plastic bag. Marinate 4-6 hours or overnight for a more intense flavor.

To prepare Herb Pesto:

Place garlic in food processor and pulse until finely chopped. Add herbs and walnuts and process. Add olive oil and process until almost smooth. Add salt and pepper.

Remove beef from marinade (discard marinade). Grill beef and pattypan squash. Slice beef and serve atop squash.