1. In a bowl, combine the yeast, sugar, and water. Let sit until foamy, about 10 minutes. Meanwhile, whisk the flour and salt together in a large bowl.
2. Add yeast mixture to the flour, then add warm milk, oil and yogurt. Stir until a dough is formed, then turn out onto a lightly-floured surface and knead until smooth, about 4-5 minutes. Transfer the dough to a large, lightly oiled bowl and cover with a damp kitchen towel or clean film. Let rise for 1 hour at room temperature, until doubled in size.
3. Meanwhile minced the garlic and roughly chop the coriander.
4. Punch down the dough and turn out onto the counter. Shape into a ball and divide into 12 equal-sized pieces. Roll each piece into a ball.
5. Heat a large, heavy bottomed skillet over medium heat. Roll each ball into 1/4-inch (1/2cm) thick. Sprinkle some minced garlic and chopped coriander, lightly press. Cook until large bubbles form on the surface, about 1-2 minutes. Flip, press gently, and cook until bubbles on the bottom are charred, 1 to 2 minutes more.
6. Brush naan with butter, stack on a plate and cover with a towel to keep warm as you cook the remaining pieces.