Prepare your pan. Line a 12-cup muffin tin with paper liners or use a silicone muffin pan. This makes removal easy and keeps the cups tidy.
Warm the wet ingredients. In a medium saucepan over low heat, gently warm 1 cup peanut butter, 2–3 tablespoons coconut oil, and 1/3–1/2 cup honey or maple syrup. Stir until smooth and just combined.
Remove from heat and stir in 1 teaspoon vanilla and 1/4 teaspoon salt.
Mix the base. Add 2 cups rolled oats to the warm mixture and stir until all the oats are coated. If you’re using add-ins like chia seeds or flaxseed meal, fold them in now.
Portion the base. Spoon the oat mixture evenly into the muffin cups. Press firmly with the back of a spoon to compact the layer.
A tight press helps the cups hold together.
Chill briefly. Place the pan in the fridge for 10–15 minutes to set the base while you make the topping.
Make the chocolate topping. In a heat-safe bowl, melt 1 cup dark chocolate chips with 2–3 tablespoons peanut butter. Do this in 20–30 second microwave bursts, stirring between each, or over a double boiler. Stir until smooth and glossy.
Top the cups. Spoon the melted chocolate-peanut butter mixture over each oat base, tilting the pan slightly if needed to spread it evenly.
Sprinkle with chopped peanuts or a pinch of flaky salt if you like.
Set completely. Chill the cups for 30–45 minutes, or until the topping is firm. Remove the liners and enjoy, or store for later.