Yields about 18 puffs

¼ cup plus 1 tablespoon rich, full-bodied red wine
¼ cup water
2 tablespoons unsalted butter, cut into cubes
¼ teaspoon fine sea salt
¼ teaspoon black pepper
½ cup all-purpose flour
3 large eggs, divided
1 cup (4 ounces) Gruyere cheese, grated and divided
Flaky sea salt
½ teaspoon fennel seed, cracked in a mortar and pestle or with the side of a knife