I used Valrhona ivoire white baking chocolate. I got it directly from my local market but you can order through Amazon if you can't find it.
You don't have to add any additional sugar because the white chocolate provides enough sweetness.
Matcha is Japanese green tea powder. I buy mine at Teavana in the Stanford Shopping Center, in Palo Alto, California. You can also find it in Korean stores or online. It's fairly expensive and has a very delicate flavor. As soon as your matcha tea box is unsealed, store it in the refrigerator or in the freezer because of its short shelf life. To check for quality, matcha should have a beautiful jade green color. If it's yellow and dull, it's time to toss it. You can use it often in baking for macarons, cakes, cookies or custards or you can turn many pastries into a nice green color. Be creative on St. Patrick's day and Halloween!
If you don't have an espresso machine, instant coffee works fine as well. There is about 1/4 cup of coffee per espresso shot, so one espresso shot is enough. You don't want the coffee to overwhelm the matcha green tea.
You can froth the milk by hand. Just place 1-1/2 cups of milk in a non-stick saucepan. It's preferable to use whole milk because the higher fat content, the foamier the milk will get. Constantly whisk the milk until it's hot. After 1-2 minutes, a generous amount of froth will form with a very small amount of hot milk at the bottom. While waiting for the milk to boil, you have to be very careful. As soon as some bubbles come up, remove from the stove and continue whisking the hot milk.
Another speedy method to froth milk is to warm it in the microwave and foam it in a blender. This works, but I think it doesn't create as much foam as the whisking version.
If you don't have a non-stick saucepan, my trick is to add a little water, wait until the water gets bubbly (not until it's evaporated though) and add milk. The cleaning of the saucepan will be much easier.
For a healthier version, you can substitute the cream and milk with hot water and milk.
For a vegan version, you can use almond, soy or rice milk and soy creamer.
For an iced tea latte version, add ice cubes.
For a smoothie version, add ice cubes and place in a blender.
For a milkshake version, add vanilla ice cream and ice cubes. Smooth it in a blender.