Spinach and Leek Gratin with Roquefort Crumb Topping

Ingredients

• 2.3 cups breadcrumbs from bread fresh french crustless
• 5 tablespoons butter divided
• 3.5 tablespoons horseradish dijon mustard divided
• 0.8 cup heavy whipping cream 
• 3 cups leek halved lengthwise thinly sliced
• 4 ounces roquefort cheese generous crumbled
• 27 ounce spinach leaves 

Equipment

• bowl
• frying pan
• oven
• pot
• sieve
• baking pan

Directions

1. Preheat oven to 400°F. Melt 3 tablespoons butter in medium skillet over medium-high heat.
2. Mix in 2 tablespoons mustard, then breadcrumbs. Sauté until breadcrumbs are golden, about 5 minutes. Cool briefly.
3. Mix in cheese.
4. Toss 1 1/2 bags spinach in large nonstick pot over high heat until wilted, about 3 minutes.
5. Transfer to sieve set over bowl. Repeat with remaining spinach. Press on spinach to drain.
6. Melt remaining 2 tablespoons butter in same pot over medium-high heat.
7. Add leek; sauté 4 minutes.
8. Add cream, remaining 1 1/2 tablespoons mustard, and spinach. Toss until thick and blended, about 2 minutes. Season with salt and pepper.
9. Transfer to 7x11-inch baking dish. Top with breadcrumb mixture.
10. Bake until bubbling, about 10 minutes.