Line an 8-inch square pan with parchment, leaving overhang on two sides for easy lifting.
In a medium saucepan over low heat, gently warm the peanut butter and maple syrup, stirring just until loosened and smooth, 1–2 minutes. Remove from heat and whisk in the vanilla and sea salt.
Stir the protein powder into the warm mixture until fully incorporated and creamy.
Place about 3/4 cup of the oats in a zip-top bag and crush with a rolling pin into a coarse meal; keep the remaining 1 cup oats whole for texture.
Fold both the crushed and whole oats into the peanut butter mixture until evenly coated. If the mix looks dry or crumbly, sprinkle in 1–2 teaspoons hot water and press with a spatula until it holds together when pinched.
Scrape the mixture into the lined pan. Press it very firmly into an even layer using a sheet of parchment and the bottom of a measuring cup. Refrigerate for 20 minutes to firm the base slightly.
Melt the chocolate chips in a dry, microwave-safe bowl in 20–30 second bursts, stirring between each, until just smooth and glossy (about 1–2 minutes total).
Pour the melted chocolate over the chilled base and spread to the edges. Tap the pan on the counter to level. Refrigerate until the chocolate is set but not rock-hard, 35–45 minutes.
Use the parchment to lift the slab out. Score the chocolate lightly with a warm knife, then cut into 12 bars. Let stand 5 minutes at room temperature for the perfect fudgy bite.