In a medium saucepan, bring 4 cups of water to a full boil over high heat.

While the 4 cups water heats, make the simple syrup: combine 1 cup 1 cup granulated sugar and 1/2 cup 4 cups water in a small saucepan over medium heat. Stir constantly until the 1 cup granulated sugar is completely dissolved, about 3–4 minutes. Do not let it boil. Remove from heat and set aside.

Once the 4 cups water reaches a full boil, remove the saucepan from heat. Add the 4 whole black tea bags, gently submerging them. Do NOT squeeze the bags. Let them steep for exactly 5 minutes — no longer, or the 4 whole black tea bags can turn bitter.

Remove the 4 whole black tea bags by lifting them out gently and letting them drip naturally. Again, do not squeeze. Discard the bags.

Pour the hot brewed 4 whole black tea bags concentrate into a large pitcher (Large). Add the simple syrup and stir to combine.

Add the 4 cups of water to the pitcher (Large) and stir well. Taste and adjust sweetness — add more simple syrup if desired.

Let the 4 whole black tea bags cool to room temperature (about 20–30 minutes), then refrigerate until fully chilled, at least 1 hour. For best results, chill overnight.

Fill tall glasses with 4 cups ice. Pour the chilled sweet 4 whole black tea bags over the 4 cups ice. Garnish with a 1 whole lemon slice and a sprig of fresh fresh mint if desired. Serve immediately.