4 fennel bulbs—fronds (leafy greens) removed and finely chopped
1/4 cup extra-virgin olive oil
4 garlic cloves, thinly sliced
1 medium red onion, thinly sliced
6 salt-packed anchovy fillets—filleted, rinsed and patted dry
4 ounces Sambuca or other anise liqueur
Bring 6 quarts of water to a boil and add 2 tablespoons salt. Set up an ice bath next to the stovetop. Blanch the whole fennel bulbs in the boiling water for 10 to 12 minutes, until fork-tender. Remove, refresh in the ice bath and drain. Cut each bulb in half.
In a 14- to 16-inch nonstick sauté pan, heat the olive oil until smoking. Add the fennel halves, cut side down, and sauté slowly until golden brown. Add the garlic and onion to the pan and turn the bulbs over. Mash the anchovies into a paste and add to the pan. Add the Sambuca and swirl through the pan, cooking until the alcohol evaporates, about 1 minute. Transfer the fennel bulbs to a platter. Add the chopped fronds to the liquid in the pan, pour over the fennel and serve.
Be careful when adding the Sambuca, an Italian anise-flavored spirit, to the hot pan. It could briefly flame up until the alcohol burns off. Adding the Sambuca while the pan is off the burner will cut the risk.