Zest and juice the orange: Use a microplane to grate the outer peel for zest, avoiding the bitter white pith. Squeeze about 2–3 tablespoons of juice.
Mix the dry ingredients: In a bowl or jar, combine 1/2 cup rolled oats, 1 tablespoon cocoa powder, and 1 teaspoon chia seeds.
Add a tiny pinch of salt to round out the flavors.
Whisk the wet ingredients: In a separate cup, stir together 1/2 cup milk, 1/4 cup yogurt, 1–2 teaspoons maple syrup, 1/2 teaspoon vanilla, 1–2 teaspoons orange zest, and the orange juice.
Combine and stir well: Pour the wet mixture over the oats. Stir thoroughly so the cocoa dissolves and no dry pockets remain.
Adjust thickness: If it looks very thick, add a splash more milk. It should be pourable but not watery; the oats and chia will thicken overnight.
Chill: Cover the jar or bowl and refrigerate for at least 4 hours, ideally overnight.
Serve: In the morning, stir and taste.
Add a drizzle of milk if needed. Top with dark chocolate shavings, extra orange zest, or orange segments for a bright finish.