In a large saucepan, bring 2 cups of water to a boil. Turn the heat off and add the tea bags, ginger, and half the mint leaves. Make sure the tea bags are covered in water. Steep the tea for 10 minutes.
Use a slotted spoon to remove the tea bags, ginger, and mint leaves from the tea. If needed, strain the tea through a fine-mesh strainer into a heatproof bowl.
Stir in the baking soda and (if using) sweetener.
Stir in the remaining 6 cups of cool water. Refrigerate until cold, for about an hour. You can also place the tea in the freezer for 30 minutes.
To serve:
Transfer the tea to a glass pitcher.
Fill drinking glasses with ice cubes and 1 or 2 thin orange slices. Pour in the tea. Garnish with mint leaves and serve.
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Notes
If your tap water has a clean taste, it's fine to use it when making this recipe. Here in Memphis, we enjoy great tap water, so that's what I use. But if your tap water tastes bad (when I lived in D.C., our tap water had a strong chlorine taste), it's best to use filtered water or bottled water.
The baking soda helps keep the tea clear and counteract any bitterness.
I use kitchen scissors to cut the string off the tea bags. This way, I can fully immerse them in hot water without immersing their tags.
You can use any type of tea that you like. I use Earl Grey tea because I enjoy its robust flavor, but you can use plain black tea, green tea, white tea, or even herbal tea.
You can use different sweeteners, including sugar, honey, maple syrup, sugar-free granulated sweeteners, or stevia. You can also use brown sugar if you take care to dissolve it fully while the tea is still hot.
You can keep the tea covered and refrigerated for up to five days. Be sure to refrain from adding fruit directly to the pitcher. Add them to individual glasses right before serving.
The nutrition info assumes that no sweetener was used.