Joi's Cooking Lemon-Ginger Poached Halibut with Leeks & Spinach

2 tsp. finely grated fresh ginger
1 tsp. finely grated garlic
Finely grated zest and the juice of 1 lemon
2 Tbs. plus 1 tsp. extra-virgin olive oil
Kosher salt and freshly ground black pepper
Four 1-inch-thick skinless halibut fillets, 6 to 8 oz. each
2 medium leeks, white and light-green parts only, halved lengthwise, rinsed well, and thinly sliced
3 cups lower-salt chicken broth or vegetable broth; more as needed
4 cups lightly packed spinach leaves, rinsed and roughly chopped
1/4 cup roughly chopped fresh mint
1/4 cup thinly sliced scallions