Trim off the stalks and fronds from the fennel bulbs, setting them aside.
Quarter the bulbs, remove the tough core, and slice them thin across the grain. You should end up with about 4 cups of sliced fennel.
Chop about 2 tablespoons of the fronds for garnish.
In a large non-stick pan, heat olive oil over medium heat. Add the sliced onion and cook until soft and translucent, about 5 minutes.
Stir in the fennel slices, sprinkle with a pinch of salt, and let them cook uncovered for about 10 minutes. The goal is to get a little caramelization on the edges.
Stir in the minced garlic, mix everything well, then cover the pan and let it cook for another 10 minutes. The fennel should be tender and slightly golden.
Add salt and pepper to taste, then garnish with the reserved fennel fronds. Serve warm.
For an extra flavor boost, a squeeze of lemon juice or a few shavings of Parmesan at the end can add extra brightness or richness.
