Preheat your oven to 375°F (190°C) and spray each cup of a standard 12-cup muffin pan with cooking spray.

Peel and thinly slice the russet potatoes into rounds about 1/16 inch thick.

In a large mixing bowl, combine melted butter, olive oil, minced garlic, chopped thyme, rosemary, sea salt, and black pepper.

Add the thinly sliced potatoes to the bowl and gently toss in the herb mixture until thoroughly coated.

Layer the coated potato slices into each muffin cup, stacking generously until filled.

Bake in the preheated oven for 45-50 minutes, rotating halfway through. They are ready when golden brown and tender.

Remove from oven and let sit for about 5 minutes before using a small spatula to lift the galettes onto a serving platter.

Garnish with fresh thyme and rosemary sprigs before serving.