Beef, broccoli and leeks are combined in a spicy, coconut-flavored curry. Serve with mashed sweet potatoes, if desired.
Combine lemongrass paste with salt and curry powder. Set aside.
Halve leeks lengthwise; cut across into 1/2-inch-wide half-circles. Place in a large bowl of cold water; swish around to release dirt. Place in colander to drain. Place steak in a bowl; sprinkle with flour. Toss to coat; set aside.
Heat oil in a large nonstick skillet over medium heat. Add curry paste; cook until fragrant, about 1 minute. Add leeks; cook, stirring occasionally, until tender, about 3 minutes. Add beef; saute until browned. Add coconut milk, water, beef stock, and broccoli. Cover; cook, stirring occasionally, until broccoli is just tender, about 5 minutes more. Uncover; cook until slightly thickened, about 4 minutes more.