In a small mixing bowl, combine milk, yogurt, protein powder (if using; see note), chia seeds, vanilla, sweetener and lemon zest and stir with a wire whisk to combine. Let sit for 5 minutes, then whisk again.
Pour into a container with a lid, cover tightly and refrigerate for at least four hours, ideally overnight. Don't worry about how runny the mixture it is initially -- it will thicken over time.
When you are ready to eat, spoon the chia pudding into a bowl. If you find the consistency too thick, add a little more milk to thin it to the desired consistency. and top with berries and chopped nuts or granola.
Without the addition of protein powder, this dish yields about 20 g protein per serving. If you make it with plant milk & yogurt, it'll contain less protein as plant milk substitutes are woefully low in this essential macronutrient.If you want more protein, I suggest adding half a serving (about 10 g protein's worth) of protein powder (if you use unsweetened, unflavored protein powder, this won't significantly affect the flavor of this dish).My favorite brand of whey protein powder is Tera's unsweetened, grass-fed, organic whey) and my favorite brand of vegan protein powder is Wilderness Poets' 60% hemp protein powder.