Making your own bitters is a labor of love, so use the highest-quality ingredients you can, such as unwaxed organic citrus and top-shelf vodka. Gentian can be found online or at some health-food stores.
Sweet potatoes are in my seasonal repertoire this time of year, so I'm always on the lookout for new ways to enjoy them. When roasting, leave the skins on for greater nutrition (and better texture). High heat muddies the fresh flavors of the herbs and lemon zest in pesto, so top it on just before serving.
Adding toasted whole-wheat breadcrumbs gives this dish a nice crunch that balances out the creaminess of the sauce. Rather than baking the shells with the crumbs on top (which can make them soggy), toast the breadcrumbs separately, and toss a handful over each serving right before you put it on the table.