Can I make this sauce ahead of time?
Yes. Mix all ingredients and refrigerate in an airtight container for up to 7 days. Flavors deepen as it sits.
What's the difference between prepared horseradish and horseradish mustard?
Prepared horseradish is pure grated root in vinegar; horseradish mustard blends it with mustard base. Both add heat and tang, but mustard adds depth.
How spicy is this sauce?
Moderately spicy with a sharp, peppery bite from the prepared horseradish. Reduce horseradish mustard to 1-2 tbsp if you prefer milder heat.
What can I serve this with besides steak?
Works well with beef roast, prime rib, corned beef, smoked salmon, or roasted vegetables.
Can I substitute Greek yogurt for sour cream?
Yes. Use full-fat Greek yogurt 1:1 for sour cream. The sauce will be slightly thicker and tangier.