In the same skillet over medium-high heat, warm 1 tablespoon oil. Add the onion and cook, stirring occasionally, until translucent, 4 to 6 minutes. Add the garlic and cook, stirring occasionally, for 1 minute. Add the fennel seeds and cook, stirring, for 30 seconds. Add the wine and cook, stirring and scraping up the browned bits, until reduced to 1/2 cup, about 2 minutes.