Whisk together the flour and salt in a large bowl. In a separate bowl beat together the eggs, milk and butter. Make a well in the flour and whisk in the wet ingredients gradually until fully combined and smooth. Cover the bowl with plastic wrap and allow the batter to rest for 1 hour at room temperature.
Preheat the oven to 400 degrees F. Grease 3 mini nonstick muffin tins. Place the tins in the oven to heat up for at least 10 minutes. Give the batter a quick stir and pour it into each muffin cup filling halfway leaving room for them to rise.
Place in the oven and do not open for 30 minutes. They should rise after 30 minutes and be golden all over. Remove from oven. Top with a thin slice of roast beef and a small dollop of horseradish on each pudding. Garnish with sprig of chive. Serve immediately.