IN large pot, melt butter and stir-fry the onions until wilted, not browned.ADD garlic, jalapeno, cumin, lentils, ginger, garam masala, salt, pepper, sugar, and bay leaf. Saute for 1-2 minutes until aromatic.
ADD the tomatoes, vinegar, and chicken stock.
BRING to a boil then lower to a simmer stirring occasionally. Cook until lentils are tender, about 1h 45 minutes.
TASTE. Adjust seasoning as needed with salt, pepper and cumin.
GARAM MASALA: (can also be found in the ethnic food aisle at most grocery stores)
IN large saute pan, combine black peppercorns, cloves, cardamom, coriander and cumin seeds, cinnamon sticks and dried red chiles. Over medium heat cook until lightly toasted, stirring constantly.
TURN off heat and stir in nutmeg.
GRIND to a fine powder in a food processor. Pass powder through a fine strainer and cool to room temp.
STORE in airtght jar and use as needed.