We've been cooking little -- aka Yukon gold or fingerling -- potatoes so they're mashed on the inside:

• Wash as many little potatoes as you feel like eating in the next three days
• Microwave 4 - 6 minutes on high (shorter for smaller) so they're just fork tender
• let them cool enough to
• toss them in olive oil (plus any spices you like)
• Place on baking sheet
• Roast along with whatever you're roasting. For us it was a 1.5 lb tenderloin.

Preheat oven to 400°F, turn down to 250° the minute you put in the roastables, roasting 1hr/pound so 1.5 hours.

The potato skins get scrumptious, caramelized and soft so they hold the mushy-mashy flesh very well.