Bring A Large Pot Of Lightly Salted Water To A Rolling Boil. Cook The Swiss Chard Stems In Boiling Water Until Tender, 10 To 15 Minutes; Drain And Rinse With Cold Water. Set Aside. Bring A Separate Large Pot Of Lightly Salted Water To A Rolling Boil. Cook The Vermicelli Pasta In Boiling Water Until Tender Yet Firm To The Bite, 4 To 5 Minutes; Drain. Meanwhile, Melt The Butter With The Olive Oil In A Large Skillet Over Medium Heat; Stir In The Onion And Garlic Scapes. Cook And Stir Until The Onion Is Soft And Translucent, About 5 Minutes. Increase Heat To Medium-High, Stir In The Chard Stalks, And Cook Until The Onion Has Browned, About 5 Minutes More. Season With Salt And Pepper; Stir In The Cooked Pasta To Serve.