Blanch the green beans. Bring a large pot of salted water to a rolling boil. Add the beans and cook 3–4 minutes until bright green and just tender-crisp. Taste a bean; it should still have a snap.

Shock and dry. Transfer beans immediately to a large bowl of ice water to stop the cooking. Once cool, drain and pat very dry with clean towels. Dry beans reheat and sauté better.

Toast the almonds. In a large skillet over medium heat, add the sliced almonds (no oil). Toast, stirring often, 3–5 minutes until golden and fragrant. Transfer to a plate to cool.

Sauté the aromatics. In the same skillet, add 1 tablespoon butter and the olive oil over medium heat. Add shallot and a pinch of salt. Cook 2–3 minutes until softened. Stir in garlic for 30 seconds until fragrant.

Build the flavor base. Reduce heat to low. Stir in Dijon, lemon zest, and 1–2 teaspoons lemon juice. Add 1–2 tablespoons water to loosen if needed. Season with salt and pepper. This mixture can be made ahead.

Make-ahead option (up to 2 days): Store blanched, dried beans in an airtight container lined with paper towels. Keep toasted almonds in a sealed container at room temperature. Refrigerate the flavor base in a small jar. When ready to serve, proceed to the next step.

Finish and serve. Reheat the skillet with the flavor base over medium heat. Add remaining 2 tablespoons butter. When melted and bubbling, add the green beans. Toss and sauté 2–4 minutes until hot and glossy. Adjust lemon, salt, and pepper to taste.

Add crunch and garnish. Fold in most of the toasted almonds, reserving a few for the top. Sprinkle with red pepper flakes and parsley if using. Serve immediately with extra lemon wedges.