Step 1
In a medium bowl, whisk together 2½ cups lukewarm water, 1 (¼-oz.) envelope active dry yeast (2¼ tsp.), and 2 tsp. honey and let it sit for about 5 minutes. After that it should start to look foamy; if it doesn’t, then it’s likely your yeast is dead and you need to get fresh yeast and start over! To the yeast mixture, add 5 cups all-purpose flour, 1 Tbsp. ground turmeric, and 1 Tbsp. salt and mix with a silicone spatula or your hands until a shaggy dough forms.
Step 2
Pour 4 Tbsp. olive oil into a very large bowl (that can fit in your fridge), add the dough, and move the dough around so that it is coated in the oil. Cover the bowl with plastic wrap or a towel and let it rise in the fridge for at least 8 hours or up to one day. You can also let it rise at room temperature for 3 to 4 hours. The dough should look quite bubbly and have doubled in size.
Step 3
Using two forks or spoons, gather the edges of the dough farthest away from you in the bowl and lift that edge over toward the center of the dough. Give the bowl a quarter-turn and repeat until all four sides have been folded toward the center. Then repeat this process 3 more times. Pour in 1 Tbsp. olive oil and make sure all of the dough is coated. Let it rise, uncovered, in a warm, dry spot for at least 1½ hours. It should double in size again. It’s ready if you press on the dough with a finger and it slowly springs back.
Step 4
Preheat the oven to 450°F. Butter a 13×9″ baking dish and pour 1 Tbsp. olive oil into the center of the pan. Pour the dough into the pan, stretching it to make sure it touches the edges, and with lightly oiled hands, dimple the focaccia all over. Think of it as putty or Play-Doh and really press down so that you can feel the bottom of the pan.
Step 5
Melt ¼ cup ghee, unsalted butter, or additional olive oil in a small, heavy-bottomed saucepan. Add 2 tsp. black mustard seeds and let them pop for 10 seconds, then remove the pan from the heat, add 4 tsp. white sesame seeds, 4 or 5 dried red chiles, and 20 to 30 fresh curry leaves, and cover the pan for a minute. Swirl the mixture, then evenly brush it onto the dimpled dough. Drizzle the dough with the remaining ½ Tbsp. olive oil and sprinkle with flaky sea salt. Bake for 25 minutes, or until the top is golden and the bread feels puffy. Cut the focaccia into squares.
Do Ahead: Baked focaccia, wrapped tightly in plastic wrap, will keep in the freezer for up to 1 month.