I discovered this exciting route "by accident" when I decided spontaneously to ascend Leahy Peak from the east. I don't know for how long the talus on the northeast ridge is protected by snow, so I can't recommend this route outside an early spring time frame. I would estimate the slope angle to exceed 35 degrees, so I suggest getting an early start to mitigate early-spring avalanche hazard.
From the city of Aspen drive west on Hwy 82 less than 1 mile to a traffic circle. Take the 3rd exit onto Castle Creek Road. Follow this road 11.2 miles to the Ashcroft ski area. This is likely where you will have to park if attempting this route. However, if the road is open past Ashcroft, continue another 0.9 miles, turn right onto Cathedral Lake Road and continue to the trailhead.
This route description assumes the Ashcroft ski area is operating. Hike south on the groomed road 0.9 miles to the Cathedral Lake Road. If you can't find the signs, just turn southwest and hike across meadows and through some aspens to reach the hillside.
Angle up through the trees to the west and follow trails where they can be found. Continue along Pine Creek, staying low on the hillside just north of the creek.
Around 10800' start to climb away from the creek west-northwest on steeper slopes. Keep climbing until you have a good view of the southeast face. Your goal is to gain the ridge directly above you to the northwest. There are many options to achieve this. Pick a line and start climbing!
Above 12400' the slopes get fairly steep. If snow conditions are poor, use the rock outcroppings (class 3) to aid your ascent. You will gain the ridge around 13000' to be welcomed by an impressive view of the summit.
Depending on your route, you may have to scramble over the narrow ridge (class 3) to reach the base of a steep, snow-covered talus field below the summit. The snow here should be fairly well consolidated. Make your way up, staying left of a huge, rotten buttress.
At the top of the talus field, scramble over a short, easy class-3 buttress, then climb the last 100' or so on good snow to the summit!
The easiest descent is via the southwest slopes.
An ice axe and mountaineering boots are all that's required. Crampons might be useful depending on conditions.