I assume that not everybody can get the intensely aromatic wild fennel, so I give you a more common substitute.
4 small or 2 large head-on mackerel (about 2 pounds) cleaned, washed and well drained
Freshly ground black pepper
6-8 sprigs wild fennel or 1 medium fennel bulb with fronds, halved and thinly sliced
2 teaspoons fennel seeds, coarsely crushed (ommit if using wild fennel)
4 cloves garlic, minced
1/2 cup white wine
Freshly squeezed juice of 1 large lemon
1 tablespoon all-purpose flour
2/3 cup extra virgin olive oil
2 small lemons, cut into thin slices
Preheat oven to 400°F.
Sprinkle fish with salt and pepper inside belly cavity and out.
Scatter 2/3 of fennel sprigs or slices and about half of seeds in a baking dish that holds fish snugly. Lay mackerels on top, stuffing their cavities with remaining fennel and seeds, and half of garlic.
In a bowl, whisk together wine, lemon juice and flour. Add olive oil and stir to blend. Pour over fish, sprinkle with remaining garlic and cover with lemon slices.
Bake for 10 minutes, and then baste with pan juices. Bake another 10 to 20 minutes, until done, depending on size of fish, basting once more with pan juices. Cover with aluminum foil and let stand for 10 minutes.
Serve warm or at room temperature.