Place a steamer insert in a large pot. Add enough water to reach the bottom of the steamer. Add in potatoes. Cover and bring to a boil; steam until tender, 15 to 20 minutes.

Meanwhile, melt 2 tablespoons butter in a small skillet over medium-low heat. Add garlic. Cook, stirring occasionally, until softened but not browned, 1 to 2 minutes. Remove from heat and let cool.

Transfer garlic butter to a mini food processor. Add remaining butter, creme fraiche, chives, and tarragon; pulse until smooth. Season with salt and pepper.

Drain potatoes and place in a bowl. Gently break open using the back of a large spoon, but do not mash. Mix in about 1/2 of the garlic-herb butter. Season with salt and pepper.