Heat vegetable oil in a saute pan over medium heat.

Add diced onion and cook for 1 minute.

Add chopped garlic, curry powder, ground ginger, ground cumin, sea salt, red pepper flakes, ground coriander, cayenne pepper, celery seed, dried tarragon, and ground cinnamon.

Cook the spice mixture until fragrant, about 1 to 2 minutes.

Add diced potatoes and frozen mixed vegetables.

Cook, stirring constantly, for 3 minutes.

Pour vegetable broth into the potato mixture.

Reduce heat to medium-low.

Cook, stirring occasionally, until potatoes are tender and broth is mostly absorbed, approximately 12 to 15 minutes.

Place all-purpose flour in a medium bowl.

Make a well in the center.

Add salt, vegetable oil, and room-temperature water, in that order.

Mix into a stiff dough.

Roll the dough into a ball and wrap in plastic wrap.

Set aside for 30 minutes to rest.

Divide the dough into 8 equal balls.

Roll each ball into a 10-inch circle.

Cut each circle in half.

Moisten the edges of each half with water.

Shape each half into a cone around your finger.

Fill each cone with 1 to 2 tablespoons of the vegetable mixture.

Pinch the edges shut to seal the samosa.

Heat oil in a large saucepan or deep-fryer.

Deep-fry samosas in batches until lightly browned, about 2 to 3 minutes.

Serve hot.