Seared venison with celeriac gratin and mushroom mustard sauce from Spice by Christine Manfield

Ingredients

• 200 g boletus mushrooms
• 300 ml Pepper Glaze
• 2 heads celeriac, peeled and diced
• 4 waxy potatoes, peeled and diced
• 1 teaspoon sea salt
• 1 teaspoon freshly ground white pepper
• 2 egg yolks
• 100 ml thick (45%) cream
• 50 ml olive oil
• unsalted butter
• 1 x 1 kg venison striploin fillet, trimmed
• 2 teaspoons freshly cracked black pepper
• 75 ml thick (45%) cream
• 1 tablespoon smooth Dijon mustard
• 3 teaspoons chopped French tarragon
• 1 tablespoon minced garlic
• 50 g unsalted butter