The phrase "extra depth" means having more understanding or knowledge about something beyond what is commonly known or expected. It's like going deeper into a topic or situation to gain a better understanding or insight. Full definition
Either way you go, don't leave out the vanilla and blood sugar - stabilizing cinnamon for extra depth of flavor that complements the fiber in the apples. (greatist.com)
A very nice selection of documentary images adds extra depth to the experience of this already very satisfying volume. (artbook.com)
Tip: For extra depth of flavor, toast the dry chickpeas first by placing them in an oven heated to 375 degrees for approximately 10 minutes before grinding. (gluten.lovetoknow.com)